When comparing gnus vs Mutt, the Slant community recommends Mutt for most people. In the question“What are the best native e-mail clients for Linux?” Mutt is ranked 2nd while gnus is ranked 12th.
Ranked in these QuestionsQuestion Ranking
Pro It supports IMAP and POP3
… but you can use DavMail to connect to Exchange server via EWS.
Pro Everything is customizable
Yep, really. From Outlook-mode, where Outlook-typical TOFU mails are “repaired”, up to a high-sophisticated scoring and SPAM filtering, footer lines with quotes, rules depending on the recipient, MIME formatting, boxquotes, etc.
Pro Terminal based
Pro Small and efficient
Pro Highly configurable macros
Pro Threads emails
Pro Active development
Even though it was first released in 1995, Mutt still enjoys an active community following it and having new releases constantly.
Pro Work with regular expressions
Mails can be filtered, deleted, flagged, etc. with regular expressions which makes mail management very efficient.
Pro Compose mails in your favorite editor
Edit mails efficiently with an editor you already can work fluently with.
Con Difficult documentation
Originally a newsgroup reader, so its documentation uses Usenet terminology for everything -- which is confusing.
It runs inside the terminal so it doesn't display HTML email, fonts, or graphical elements.