For the past years I used mutt as my one and only email client. Recenty, as I changed my complete email structure and moved from mbox to IMAPs, I also took the opportunity and chose to change my MUA to be Mozilla Thunderbird. Dumb move, I should have anticipated that..
Being honest it definitely is another feeling: Grafical presentation of emails, even HTML-Mails were now readable without any extra activity! I used Thunderbird 0.7 through 1.0 - and every single one sucked when it came to using it on a daily basis. I did not count how many times I had to restart Thunderbird or how many unsent emails I lost when it crashed.
Being sick of it I returned to use the good and stable mutt, even while it still lacks some functionality it is probably the most usable MUA available.
To set up mutt to use IMAPs and aSMTPs do the following:
extern Bool UseTLS;
extern Bool UseTLSCert;
extern char *TLSCert;
Afterwards add another line to your ~/.muttrc:
set sendmail="/usr/bin/ssmtp -au username -ap password"
( This of course is an although easy but very bad approach, saving the password in plaintext is actually not a good choice and you should not do that. At least chmod 0600 the .muttrc file. I instead patched the ssmtp-source so the binary already contains my password, but thats not an improvement, as it still is saved in clear text )
Unfortunately, ssmtp is an abandoned project. And its successor bssmtp is sadly not maintained anymore, either. It works fine, though.