|laziness, impatience, and hubris|
Neomail pales in comparison to Openwebmail. Openwebmail runs setuid - true. However, you can wrap the setuid with C and it is perfectly safe. As a matter of fact, the FreeBSD port does this automatically on install.
Openwebmail does not support IMAP or maildir. Not sure if this is an issue.
It is fast and has a very nice interface. Everything is configurable very easily. You can turn off the webdisk for all users or on a per user basis. You have the same control over almost all features. The forum and development is active and helpful and the changelogs are current. Setup is as easy.
I've used OWM for 3 years very happily. It has very good MIME support and also allows composing HTML messages via HTMLArea, built in. It has many many features that are very nice. I highly recommend reading the features link and checking it out. Tons of language support.
Take notice that the screenshots on the site are old. The program looks much different than that currently.
Also, vCard support and a full featured addressbook are coming soon according to the forum...
blahblah (yes, I'm biased)