When comparing Mu4e vs Squirrelmail, the Slant community recommends Mu4e for most people. In the question“What are the best self-hosted webmail clients?” Mu4e is ranked 6th while Squirrelmail is ranked 8th. The most important reason people chose Mu4e is:
The UI is designed to allow for quick keystrokes to get around and is pretty clean. Header View: !(http://www.djcbsoftware.nl/code/mu/mu4e-2.png) Message View: !(http://www.djcbsoftware.nl/code/mu/mu4e-3.png)
Ranked in these QuestionsQuestion Ranking
Pro Can write rich text emails
Using the (beta) org mode, Mu4e can compose fully rich text emails.
Pro Built-in Autocomplete
Doesn't require you to import address books for autocomplete, learns from your emails just like Gmail.
Heavy actions never block emacs, unlike most other emacs email clients.
Pro Fully Search Based
Mu4e has no folders or other organizational tools, rather it relies on very fast search queries to help you find your mail.
Pro Very mature
Squirrelmail has been around for a long time.
Pro Has many available plugins
Can do things like change Linux user passwords, configure vacation "out of office" messages, configure procmail .forward files, etc.
Con Very old
Squirrelmail has been around for a loooooong time!