Other features include encrypted storage, whitelisting, powerful HTML editor, attachment viewer, message drag and drop, custom message templates, SSL encryption or USB flash drive installation.

Key Features:
Clyton can be installed to a USB flash drive (a.k.a. thumb drive, memory stick). This allows you to run Clyton from any computer.
Built-in address book supports custom fields and import / export.
Send personalized mass mail to a filtered set of address book contacts.
Supports text search in a single folder or globally.
Whitelisting prevents false positives by the spam engine. Whitelisted senders and address book contacts are never treated as spam.
Supports message templates with merged fields.
Message drag & drop supported.
Attachment viewer supports a wide variety of image formats, HTML, and MIME. Images can be zoomed in and out.
Multithreaded design keeps the user interface responsive. Receiving, sending, and spam checking are performed in the background by worker threads.
Compose email formatted in HTML with a powerful editor. Includes spell-checking.
Supports both POP3 and IMAP4 mail server protocols.
Works with Gmail and Yahoo.
Messages can be organized in folders and color coded.
Multiple messages can be selected with the Shift and Ctrl keys. The following features can operate on multiple messages: Delete, Forward, Redirect, Save, Shred, Drag & Drop, and Color Coding.
The Forward and Redirect features support multiple destination addresses.
Old messages can be automatically deleted (by age or count) from the Trash and Spam folders.
Attachments can be automatically included in newly composed messages.
Reminds of birthdays and anniversaries.
Highly configurable user interface.