Sylpheed adopts 3-paned display similar to the popular e-mail clients for Windows such as Outlook Express and Becky.The user-interface is comfortable operational.

Stability and the protection of data is taken into account to the fullest extent. Storing several thousand messages doesn't affect the stability. Even if the application is forcibly terminated, there is almost no possibility of the lost of mail, or inconsistent state of mailboxes.

Sylpheed supports not only the major protocols such as POP3, IMAP4rev1 and SMTP, but also NNTP (NetNews) but also IPv6, which is the next-generation Internet protocol. Sylpheed optionally supports the signing and encryption of messages by GnuPG, and the encrypted communication of POP3/IMAP4/NNTP over SSL/TLSv1.

Sylpheed has a powerful search function which utilizes this filtering engine. Moreover, you can easily refer to the messages which matches search conditions by saving the result as a search folder. It also has the quick search function which quickly narrows down the message list by flag types and subject strings.

Sylpheed has a learning-type of junk mail control which utilizes external commands. You can automatically filter junk mails without setting filter rules by hand, so you don't have to worry about being buried in the flood of junk mail anymore. It also has high flexibility. Other than the bogofilter and bsfilter, which are the default, you can use any programs as the external commands. The preset commands are available, so you can easily make use of it.