This pull request introduces several improvements and new features to the mail handling modules, expands Linux packaging options, and updates dependencies. The most significant changes are the introduction of new IMAP mailbox management functionality, new mail node types, and enhancements to the Linux build configuration.

Mail and IMAP functionality improvements

• Refactored IMAP session management in imap.rs: Added ImapSessionCache with methods for mailbox creation and existence checks, and updated session retrieval logic to use to_session and to_session_cache methods, improving caching and code clarity. [1] [2] [3] [4]
• Added new mail node types in mail/imap/inbox/mail.rs: Introduced ToMailReferenceNode and registered new nodes for draft creation, mail moving, deletion, marking as seen, and copying, expanding mail processing capabilities. [1] [2] [3]

User experience enhancements

• Added dynamic mail footers: Implemented functions to generate rotating plain text and HTML footers for outgoing mail, enhancing branding and user engagement.

Linux build and packaging

• Updated Linux build configuration: Added RPM packaging options with no compression and included new binary libmtmd.so in the Linux build manifest, improving deployment flexibility. [1] [2]

Dependency updates

• Added base64 crate to several Cargo.toml files, preparing for future encoding/decoding needs in mail and catalog packages. [1] [2]

UI consistency

• Updated node icons in mail nodes to use a consistent mail icon, improving visual coherence in the UI. [1] [2] [3]

Let me know if you'd like a deeper dive into any of these areas!