Linux Mail Client Defined :

A Linux mail client is a local application that lets you manage emails on a Linux system using protocols like IMAP, POP3, and SMTP. It connects to mail servers to send and receive messages, often supporting advanced features like PGP encryption, MIME attachments, filtering rules, and offline access. Some clients like Thunderbird offer a full GUI with calendars and contact integration, while others like Neomutt run in the terminal with deep customization, scripting, and mailbox control. These tools are ideal for users who need technical flexibility, privacy, and system-level integration beyond what webmail can offer. 

When choosing the best Linux mail client, you should look at a few critical technical parameters to match your workflow, system, and email needs. Here are the most important ones:

1. Protocol Support
   Check if it supports IMAP, POP3, and SMTP, so it can connect to your mail server correctly. For enterprise use, Exchange Web Services (EWS) support is crucial.
2. Encryption & Security
   Look for built-in or plugin support for PGP, S/MIME, and SSL/TLS. This ensures encrypted communication, secure server connections, and protection of email content.
3. Resource Usage
   Measure RAM and CPU usage, especially for older systems. Lightweight clients like Claws Mail or Neomutt are ideal for low-resource setups, while heavier ones like Evolution suit modern desktops.
4. User Interface
   Choose between GUI-based clients (e.g., Thunderbird, Mailspring) for ease of use, or CLI-based clients (e.g., Neomutt) for speed, scripting, and terminal control.
5. Mail Storage Format
   Know whether it uses Maildir, mbox, or a database-backed system. Maildir is safer for concurrent access; mbox is simpler but older.
6. Search & Filtering
   Advanced search indexing, filtering rules, and regex support make it easier to manage large volumes of email efficiently.
7. Extension & Plugin Support
   Some clients support plugins or add-ons to extend functionality, like calendars, task lists, or encryption modules (e.g., Thunderbird add-ons or Claws Mail plugins).
8. Desktop Environment Integration
   Ensure compatibility with your desktop (GNOME, KDE, XFCE). Evolution integrates well with GNOME; KMail is built for KDE.
9. Synchronization & Offline Access
   Check if it supports offline IMAP sync, local caching, and conflict handling when working without an internet connection.
10. Active Development & Community
    Choose a client that is actively maintained, receives updates, and has community or developer support for troubleshooting or bugs.

✅ Covered Use Cases

Linux Mail Clients Comparison Table

#1 Thunderbird– The Most Balanced and Feature-Rich Linux Mail Client

If you're using Linux and want an email client that just works—while also being powerful, secure, and customizable—Thunderbird is hands down one of the best picks. It’s developed by the Thunderbird Council (independent but closely tied to Mozilla), and it gets regular feature-packed updates, making it a rock-solid choice for both casual users and professionals. The interface is familiar and user-friendly, but underneath it has serious power.

Key Features

1. Protocol Support:
   Supports IMAP, POP3, and SMTP natively. Also connects to Microsoft Exchange and Office365 via optional add-ons like Owl or ExQuilla, using EWS (Exchange Web Services).
2. Encryption & Security:
   Now comes with built-in OpenPGP support (no need for Enigmail), enabling end-to-end encryption, key management, and digital signing. Also supports S/MIME certificates and enforces SSL/TLS for secure connections.
3. Add-ons & Extensibility:
   Thunderbird has a huge ecosystem of add-ons, including calendar (via Lightning), task managers, themes, mail merge, AI-based spam filtering, and more.
4. Advanced Search & Filters:
   Features a global search index, supports tags, filters per account, and even regex-based rules. You can automate cleanup, sort by custom rules, or prioritize threads.
5. Mail Storage Format:
   Supports both mbox (default) and Maildir (experimental, one-file-per-email). Maildir is preferred for large mailboxes or backups.
6. Multi-Account Support:
   Easily handles multiple email accounts, even with different identities, SMTP servers, and settings.
7. Cross-Platform UI:
   Built using XUL and GTK on Linux. Works on Windows, macOS, and Linux alike. Integrates with system notifications, spellcheck, calendar pop-ups, and more.
8. Offline Use:
   Thunderbird can fully cache mail locally, meaning it works perfectly offline and syncs once you're back online.
9. Regular Updates:
   The recent Supernova (v115) redesign brought major performance, UI, and threading improvements. Thunderbird 2025 roadmap includes better mobile sync and web client experiments.

🆚 Thunderbird vs Others — Quick Comparison

1. Thunderbird scores high on protocol support, security, extensions, and multi-account handling
2. Evolution is great for GNOME users and Exchange support, but uses more memory
3. Claws Mail is lightweight and fast but lacks modern UI
4. Mailspring has a sleek UI but lacks encryption and POP3

Final words

If you want one email client that can do it all on Linux, Thunderbird offers the best balance of features, extensibility, privacy, and performance. It scales from basic users to developers, system admins, and even corporate environments when configured with Exchange plugins.

#2 Mailspring – A Sleek, Modern Mail Client with Unified Inbox and Smart Features

If you’re after a polished, fast, and modern-looking email client for Linux that works out-of-the-box with multiple accounts, Mailspring is a solid pick. It blends a minimalist design with just enough advanced features to feel powerful without being overwhelming. Built on Electron, it's lighter than you’d expect and especially appealing for users who want a clean experience without deep customizations.

Technical Highlights 

1. Unified Inbox
   Mailspring supports a unified inbox that merges all your email accounts—Gmail, Yahoo, Outlook, custom IMAP—into one smart stream. It supports IMAP and SMTP, but does not support POP3, which may be a blocker for some setups.
2. Advanced Search
   It offers blazing-fast search powered by local indexing and optional server-side search for IMAP. You can filter by contact, subject, date, or even phrase with predictive results.
3. Touch & Mobile-Ready UI
   Built with Electron, Mailspring uses a responsive layout and supports touchscreens, making it perfect for laptops and hybrid devices.
4. Productivity Features
   In its Pro version, it includes read receipts, link tracking, send later, and email templates—great for freelancers or small businesses.
5. Encryption & Security
   It supports SSL/TLS encryption for IMAP and SMTP connections. However, it does not support OpenPGP or S/MIME, meaning it’s not the best pick for secure communications.
6. Cloud Sync
   Mailspring stores your accounts and preferences using its own cloud-based sync engine—great for syncing across machines but raises privacy considerations.
7. Mail Storage Format
   Uses SQLite database for storing cached mail and metadata. It’s not using mbox or Maildir, which limits portability for some backup workflows.
8. Extensions & Customization
   While it has theming options, Mailspring does not support plugins or scripting. What you see is mostly what you get.
9. Offline Mode
   Fully functional offline. Mailspring caches your mail locally so you can read and compose offline, syncing changes once reconnected.

🆚 Quick Comparison: Mailspring vs Thunderbird

Ideal Use Case

If you want a Gmail-like experience on desktop with modern visuals, productivity features like send later and tracking, and don't need deep customization or encryption—Mailspring is perfect. Especially great for casual users, marketers, or freelancers juggling multiple inboxes.

#3 Evolution – The Best Outlook Replacement for Linux with Full Exchange Support

If you're looking for a serious, all-in-one alternative to Outlook on Linux, Evolution is the closest match. It’s more than just an email client—it’s a complete Personal Information Manager (PIM) with email, calendar, tasks, memos, and contacts rolled into one. Built with GNOME users in mind, Evolution feels right at home on Fedora, Ubuntu GNOME, and other GTK environments. It’s powerful, secure, and tightly integrated with enterprise features like Exchange Web Services (EWS).

Technical Breakdown

1. Full PIM Functionality
   Evolution isn't just mail—it handles contacts, calendars, task lists, memos, and integrates them natively with your GNOME desktop.
2. Native Exchange Support
   It supports EWS (Exchange Web Services) natively, allowing full access to calendars, shared folders, GAL (Global Address List), and meeting invites—no plugins required.
3. Encryption Support
   Comes with GPG/PGP integration (via GnuPG and GPGME) for signing and encrypting messages. S/MIME support is also included for enterprise-grade certificate-based encryption.
4. Search & Filtering
   Evolution has a powerful search engine, with indexed results and rule-based filtering. You can set custom mail rules per account, per folder, and even automate cleanup.
5. Mail Storage Format
   Uses Maildir++ (one-file-per-message) for better performance on large inboxes and easier backups than the older mbox format.
6. System Integration
   Deep GNOME integration: uses GNOME Online Accounts, system notifications, native address book, calendar reminders, and even syncs with Flatpak sandboxed accounts.
7. Offline Access
   Fully functional offline: cached mail, calendar entries, and tasks are accessible even without a connection.
8. User Interface
   Classic, split-pane UI with tabbed mail view. It's functional, but not the most modern-looking—ideal for those who prioritize power over visuals.
9. Resource Usage
   Can be heavy, especially with large Exchange accounts and background calendar indexing. Not ideal for low-memory systems.

🆚 Evolution vs Thunderbird – Side-by-Side

Ideal Use Case

If you’re in a corporate or enterprise environment and need full Exchange access with calendar sync, task integration, and PGP support, Evolution is your go-to. It’s especially great for GNOME desktop users looking for tight OS integration and a productivity-focused experience.

#4 Claws Mail – The Lightweight, Plugin-Friendly Linux Mail Client for Power Users

If you want an email client that’s snappy, lean, and highly customizable without the bloat of modern UI frameworks, Claws Mail is a fantastic choice. It’s built for speed and precision, making it a top contender for older hardware or minimal desktop setups. It doesn’t try to be a full PIM or calendar system—it does email, and it does it really well. Lightweight but not limited, it gives you serious filtering tools and plugin flexibility for power users.

Technical Insights

1. Performance First
   Written entirely in C, Claws Mail is exceptionally fast and uses very low memory and CPU. Perfect for legacy hardware or systems where performance is key.
2. Protocols Supported
   Supports IMAP, POP3, SMTP, and SSL/TLS encryption. No built-in support for Exchange or EWS.
3. Plugin System
   Extend Claws Mail with dozens of modular plugins:
1. HTML rendering (via Dillo or LiteHTML plugin)
2. RSS reader
3. PDF viewer
4. SpamAssassin or Bogofilter for spam filtering
5. GPG for message encryption and signing
4. Filtering & Automation
   Powerful rule-based filtering engine with regex support, folder-specific rules, and script execution. One of the best filtering systems in any Linux client.
5. UI & Layout
   Clean and simple GTK+ interface, with no unnecessary flair. Uses a classic 3-pane view that is highly responsive.
6. Encryption Support
   PGP (via GnuPG) supported through plugin, along with S/MIME (optional). Not enabled by default—users must configure and install manually.
7. Mail Storage Format
   Uses MH format by default, where each message is a separate file. Supports Maildir and mbox import/export.
8. Offline Support
   Fully functional in offline mode—especially with POP3 mail or cached IMAP. You can queue messages and sync when back online.
9. Customization
   High level of control over headers, display options, toolbars, and mail handling. Also supports scripting via external commands.

🆚 Claws Mail vs Thunderbird – Technical Comparison

✅ Ideal Use Case

Claws Mail is perfect for:

1. Users on low-powered systems
2. Those who want speed and simplicity
3. Power users who need advanced filtering
4. Email-only workflows (no calendar or task features)

If you prefer a simple, fast, and customizable email experience that doesn't rely on heavy frameworks, Claws Mail delivers with precision.

#5 Geary – A Clean, Minimal Email Client for Everyday Users

If you’re looking for a Gmail-like email experience on your Linux desktop with a clean interface and conversation-style layout, Geary is a solid pick. It’s built for simplicity and speed, not feature overload. Geary is perfect for users who want to check and respond to emails without diving into advanced filters, plugins, or encryption setups. It’s especially well-suited for GNOME-based systems and beginner Linux users.

Technical Overview 

1. Modern Conversation View
   Geary organizes emails by thread, similar to Gmail. It offers a tidy, distraction-free interface focused on reading and replying to conversations.
2. Supported Protocols
   Supports only IMAP and SMTP. POP3 is not supported, which means you must keep mail on the server.
3. Encryption & Security
   Basic SSL/TLS encryption is supported for connections, but PGP or S/MIME encryption is not available. This makes it unsuitable for privacy-focused or sensitive communication.
4. Search & Filters
   Offers basic full-text search. No support for server-side filtering or complex mail rules.
5. UI & GNOME Integration
   Built using GTK, Geary integrates beautifully with GNOME environments. It works great with GNOME Online Accounts, letting you add Gmail and other services quickly.
6. Performance
   Very lightweight. Low memory usage, fast startup, and responsive UI even on slower systems.
7. Mail Storage Format
   Uses a SQLite database to cache mail locally. No standard mbox or Maildir export.
8. Extensions & Customization
   Geary does not support plugins or extensions. The design philosophy is minimalism and usability over customization.
9. Offline Access
   You can read and write emails offline, and they’ll sync when you reconnect. However, Geary does not store full mailbox copies by default like Thunderbird.
10. Development Status
    Actively developed under the GNOME project, but progress is conservative—expect small, stable improvements over radical changes.

Geary vs Thunderbird – Key Comparison

✅ Ideal Use Case

Geary is great if you:

1. Use GNOME desktop and want something native
2. Prefer a Gmail-like interface
3. Don’t need encryption, filtering, or plugin support
4. Want a simple, fast email client for day-to-day use

#6 Mutt / NeoMutt – The Ultimate Terminal Mail Client for Power Users

If you're living in the terminal or just prefer keyboard-driven tools, Mutt and its enhanced fork NeoMutt are unbeatable choices. These clients are fast, lightweight, and extremely customizable. Unlike modern GUIs, Mutt/NeoMutt run right in your terminal window, and once configured, they can become a powerful center for managing email—especially for developers, sysadmins, and keyboard-first users.

Technical Deep Dive

1. Interface & Workflow
   Purely text-based and keyboard-driven, Mutt and NeoMutt offer a ncurses interface. You navigate threads, open messages, reply, and sort—all via the keyboard. There's no mouse support, which for terminal purists is a plus.
2. Protocol Support
   Supports both IMAP and POP3 through integration with external fetchers like fetchmail, isync/mbsync, or offlineimap. Sending is done via built-in SMTP or external sendmail/postfix.
3. Offline Mail Access
   You can set up Maildir or mbox as local mail storage. With syncing tools like isync, you can fully cache your mailbox and use it completely offline, syncing back changes later.
4. Highly Configurable
   Every keybinding, folder path, header view, and macro can be customized via .muttrc or .neomuttrc. NeoMutt adds support for notmuch, index colorization, sidebar view, and even mail tagging.
5. Encryption
   Full support for PGP/GPG and S/MIME, integrated with GnuPG. You can sign, encrypt, and verify messages inside the terminal.
6. Attachments & HTML Emails
   Mutt relies on external tools:
1. w3m, lynx, or elinks for HTML email rendering
2. xdg-open, muttprint, or custom scripts for attachments
   This modularity gives total control, but adds setup complexity.
7. Mail Filtering
   Mutt doesn't do filtering by itself. Instead, you pipe messages through tools like procmail, maildrop, or sieve. This is extremely powerful when combined with shell scripting.
8. NeoMutt Enhancements
   NeoMutt adds modern features like sidebar, threading, multiple accounts, and easier support for OAuth2, making it more user-friendly than classic Mutt.

NeoMutt vs Thunderbird – Terminal vs GUI Comparison

✅ Ideal Use Case

NeoMutt is perfect if you:

1. Prefer working in the terminal
2. Need fine-grained control and deep automation
3. Want an ultra-lightweight mail setup
4. Are comfortable configuring your own workflows

It’s not ideal for casual users, but for terminal-focused professionals, it’s one of the most powerful email clients available.

#7 KMail – The Power-Integrated KDE Mail Client with Akonadi and PIM Suite

If you use the KDE Plasma desktop and want a mail client that blends in perfectly while offering powerful features under the hood, KMail is your go-to. It’s part of the Kontact Suite, KDE’s answer to a full PIM system, which includes email, calendar, contacts, feeds, notes, and more. While it requires some setup and can be heavy due to its backend (Akonadi), KMail offers deep customization, strong security support, and great KDE integration.

KMail Technical Deep Dive

1. Protocol Support
   Supports IMAP, POP3, SMTP, and Exchange via Akonadi EWS resource. Ideal for both personal and enterprise environments.
2. Encryption & Signing
   Offers complete PGP/GPG and S/MIME integration through Kleopatra, KDE’s native key manager. Supports digital signing, encryption, and key management.
3. Mail Storage Format
   Uses Maildir format for local storage (one-file-per-email), optimized for indexing and offline access. Fully backed by Akonadi, which handles background sync and metadata.
4. Advanced Features
1. Powerful search and filters through Akonadi’s full-text indexing
2. Email templates, tagging, read receipts, color labeling
3. Inline spell-checking, external editor support
4. Smart address autocompletion and identity management
5. Desktop Integration
   Seamlessly ties into KDE services like KWallet (secure password storage), Plasma notifications, and KOrganizer for calendar events.
6. Offline Mode
   Yes — KMail caches mail locally and works fully offline. You can compose, sort, and read without connectivity.
7. Plugins and Customization
   Supports internal plugins (antivirus, spam control, etc.), plus themes, UI tweaks, and script integration.
8. Resource Usage
   Medium to high, due to the Akonadi backend and indexing services. It’s best suited for modern desktops, not minimal systems.
9. Development Status
   Actively maintained as part of the KDE Gear project. Gets regular updates, especially tied to Plasma releases.

KMail vs Thunderbird – Feature Comparison

✅ Ideal Use Case

KMail is best suited for:

1. KDE Plasma users wanting native integration
2. Users who need Exchange access and PGP/S/MIME security
3. Those managing calendars, contacts, and emails in one place
4. People looking for a powerful desktop email client with offline mode and deep settings

#8 Trojitá – A Super-Fast IMAP Client for Simplicity and Speed

Trojitá was built with a clear goal: offer a lightweight, efficient IMAP email client with modern performance and clean code. It’s ideal for users who need fast access to IMAP accounts without the overhead of full PIM suites. While its development has slowed in recent years, Trojitá remains a great fit for embedded systems, custom distros, or users who prioritize speed, minimalism, and low resource usage.

Technical Insights (Deep Dive)

1. Protocol Support
   Fully supports IMAP (IMAP4rev1) and SMTP, but does not support POP3. This limits use to server-stored mailboxes only.
2. Encryption
   Uses SSL/TLS for encrypted connections. It can verify and decrypt PGP and S/MIME messages, but does not allow composing encrypted emails—read-only support for secure content.
3. Mail Storage
   Does not maintain a traditional local mailbox. Instead, it dynamically pulls data from the IMAP server and uses on-disk caching only when configured. No support for Maildir or mbox formats.
4. Performance
   Built using Qt, Trojitá is extremely lightweight and optimized for speed and low memory usage. It opens quickly, handles large mailboxes fast, and scales well even on limited hardware.
5. User Interface
   The interface is minimal and functional, following Qt design standards. It's not flashy, but it’s very responsive and fits well in low-resource desktops.
6. HTML Email Viewing
   Supports basic HTML rendering natively, with the option to display HTML as plaintext or limited formatting. No plugin-based rendering engine like Thunderbird.
7. Features and Customization
   Focused on core functionality—there are no plugins, extensions, or themes. Trojitá prioritizes clean, predictable behavior with few distractions.
8. Offline Access
   Has limited offline capabilities. With proper IMAP caching enabled, previously accessed emails are available offline. However, it is not designed for complete offline workflows.
9. Development Status
   Development has slowed significantly in recent years. While still functional and useful, it’s not actively evolving or gaining new features. 

Trojitá vs Thunderbird – Lightweight vs Full-Featured

✅ Ideal Use Case

Trojitá is best suited for:

1. Low-resource devices (e.g., Raspberry Pi, old laptops)
2. Users who just want fast IMAP access without bells and whistles
3. Custom Linux distributions where footprint and simplicity matter
4. Developers embedding mail features into Qt-based environments

If you want a lightning-fast IMAP client with zero clutter, Trojitá is excellent. But if you need encryption, POP3, offline-first design, or plugins—Thunderbird is a better fit.

#9 Sylpheed – A Lightweight, Stable Mail Client for Classic Desktop Workflows

Sylpheed is a no-frills, fast, and reliable email client for Linux (and other platforms) built using GTK+. It’s ideal for users who value simplicity, speed, and low memory usage over fancy visuals or modern integrations. Think of it as a minimalist version of Claws Mail—it’s actually the original project from which Claws was forked, so their design is similar, but Sylpheed has taken a more conservative, stable development path. It’s perfect for those who just want a lightweight, stable email client that works.

Technical Details (In-Depth)

1. Protocols Supported
   Full support for IMAP, POP3, and SMTP protocols with SSL/TLS encryption for secure communication.
2. Encryption Support
   Offers PGP support via GnuPG, but it’s not integrated by default—you’ll need to configure it manually. S/MIME is not supported natively.
3. HTML Email Handling
   Sylpheed does not support full HTML rendering. It displays the plain-text alternative and shows a notification if HTML content is present.
4. Filtering & Search
   Comes with basic rule-based filtering, which works well for simple tasks like moving emails to folders. It supports searching by headers, subject, sender, and date, but lacks full-text or indexed search.
5. Mail Storage Format
   Uses MH format (one-file-per-message), which is efficient and reliable. It makes archiving and backups easier, especially on traditional mail setups.
6. Performance & Footprint
   Very low memory usage and fast startup time, even on older machines. This makes it suitable for lightweight Linux distros and embedded environments.
7. UI & Interface
   Traditional 3-pane layout, very similar to Claws Mail. It’s clean, functional, and intentionally old-school. No theming or skinning support.
8. Customization & Extensibility
   Very limited customization. Unlike Claws, Sylpheed has no plugin system. What you see is what you get—stable, predictable, and lightweight.
9. Offline Access
   Supports offline reading and composing, especially with POP3 and cached IMAP folders. Syncs back when connected.
10. Development Status
    Still maintained but with very infrequent updates. It focuses on bug fixes and long-term stability, not new features.

Sylpheed vs Thunderbird – Lightweight vs Full GUI

✅ Ideal Use Case

Sylpheed is best if you:

1. Are using older hardware or lightweight Linux distros
2. Need a simple, stable client with minimal configuration
3. Prefer text-based email workflows and don't care about HTML or encryption features
4. Want something you can "set and forget" that just works

It’s not for everyone, but for old-school users, offline POP3 usage, or simple IMAP setups, Sylpheed remains a dependable classic.

#10 Tutanota – A Privacy-First, Encrypted Email Client Built for Security

If your top priority is email privacy and security, Tutanota is a standout. Unlike traditional Linux mail clients that rely on IMAP/SMTP/POP3 protocols, Tutanota is a fully integrated encrypted email platform with its own proprietary system. It’s not a drop-in replacement for Thunderbird or Claws Mail—but it’s perfect for users and teams looking to escape surveillance, track-free communication, and centralized email hosting without needing PGP configuration.

Technical Deep Dive

1. End-to-End Encryption
   All Tutanota emails (including subject lines, body, and attachments) are end-to-end encrypted by default. It uses a custom encryption stack based on AES-128 and RSA-2048, not traditional PGP, which allows for seamless key exchange and automatic encryption—even with external recipients.
2. No IMAP/POP3/SMTP Support
   Tutanota is a closed system—it doesn’t support integration with third-party email clients via IMAP or POP3. You must use their official apps or web interface, which are open-source but tightly bound to their infrastructure.
3. Interface & Clients
   Available as a web app, Electron-based desktop client, and Android/iOS mobile apps. The UI is modern, sleek, and built for usability. It supports threaded conversations, folder structure, search, dark mode, and multi-account support.
4. Search Functionality
   Because mail is encrypted, Tutanota performs client-side, encrypted full-text search. It temporarily decrypts an indexed cache to allow fast local searching.
5. Calendar & Contacts
   Includes an encrypted calendar and contacts management, both of which maintain Tutanota’s strict no-tracking, privacy-first design.
6. Offline Support
   Offline mode is available in the desktop and mobile apps. Cached mail is stored securely and encrypted on local storage.
7. Security Extras
1. No IP logging
2. No advertisements
3. Two-factor authentication (2FA)
4. Custom domain support (paid plan)
5. GDPR and German privacy law compliance
8. Encryption Transparency
   Fully open-source on GitHub, including client code and cryptographic routines. The server side is proprietary but heavily audited.
9. Limitations
1. Cannot integrate with other mail clients or servers
2. No plugins or extensions
3. Some features like custom domains, catch-all, white-labeling are paid-only
4. Not suited for users needing traditional protocols or complex automation

Tutanota vs Thunderbird – Privacy Platform vs Full Mail Client

✅ Ideal Use Case

Tutanota is best for:

1. Privacy-focused users who want automatic, full encryption without configuring keys
2. Activists, journalists, or security-conscious teams
3. Users who prefer dedicated apps over protocol-based integration
4. Anyone looking for a simple, secure, and ad-free email solution

Not suited for:

1. Users needing IMAP integration, plugin systems, or custom scripting
2. Complex enterprise mail workflows with automated mail routing