• Spell checking (squirrelspell)
• Mail filters (filters)
• Web-based administration of SquirrelMail (administrator)
• A calendar (calendar)
• An interface to submit bug reports semi-automatically (bug_report)

Examples of functionalities added by various third-party plugins include:

• Address book/contact grouping and other address book expansions
• Monitoring and security tools to track usage, fight attackers and improve security
• Password change
• Quota reporting
• Rich text (HTML) email composition and display
• User-configurable front-ends for autoreponders, spam filtering systems such as SpamAssassin and server-side mail filters
• Weather reporting