Lately I decided to leave my current mailclient Clawsmail and switch to a web-based solution. A requirement was to be able to intall it on a hosted webspace (Hosteurope in my case). Furthermore it should provide threaded views and filters to handle mailinglists. A quick search brought me the following candidates which I will discuss in detail below. All these webmailers are written in PHP and licensed under the GPL.
Because it has little requirements installation should be easy. In fact there is a Perl configuration script which can't be run on most shared webspace, but I guess configuration can be done manually too. I haven't tried though, since Hosteurope already provides a SquirrelMail frontend to their customers.
Basic filtering is provided by SquirrelMail by coloring matching messages accordingly in different colors. However I prefer to have my filtered mails moved to proper folders. Possibly you could use a plugin to achieve this, but recently SquirrelMails webserver got compromised and they hold on access to the plugins for security reasons.
Not as popular as SquirrelMail, but rock solid and base of several other webmailers. In contrast to SquirrelMail it also supports POP3 in case you need it. While it nicely installs on a hosted webspace (MySQL is needed) it does not have any filtering capabilities which is a showstopper for me. Anyway I wanted to mention it here, because the following last two webmailers are based on IlohaMail.
It can display Images and HTML inline if you want. Searching messages is implemented (requires IMAP) and multiple identities are supported. Personally I really like the way the contacts list is arranged and find it very easy to create new contacts from received mails. The builtin calendar and bookmark manager are very basic.
Pretty webmailer based on IlohaMail and effectively has the same features but with much more eyecandy. It makes use of the latest web technology like XHTML, CSS2, AJAX and allows composing of messages with Richtext/HTML. Wether this is good or not, is up to you. Hosteurope now offers RoundCube as an alternative to SquirrelMail to their customers.
The last webmailer I tried (also based on IlohaMail) finally gave me what I was looking for. Well, I have to say almost. BlueMamba shows messages in a threaded view and allows for basic filtering, that is great. It isn't quite easy to install though. After some tinkering I finally had it working.
BlueMamba has a nice and clean user interface. Basic filtering is supported, enough to sort out incoming mailinglists. It features the nice contacts list from IlohaMail and has a improved calendar and bookmark manager.
As you may expect, BlueMamba has become my favourite webmailer. I think it has potential and at least is sufficient for my needs. I think I will write down how to install BlueMamba on a hosted webspace on post on this blog later.