thunderbird replacement

[Aryeh Friedman]

I currently am using mail/thunderbird as my mail reader and it is just
doing the job very well (even with heavy use of filters).... I use
xfce4 on 8.1-PRERELEASE (updated and portmaster -Rafd'ed about 3 weeks
ago).... I am looking for a good replacement suggestions.... here are
the minimal features I need:

* Gmail support
* Filtering (either internal or via external tool)
* Multiple accounts (2)
* Ability to send via local sendmail (my ISP blocks incoming port 25
thats why I am using gmail)
* Handle over 1000 messages a day
* (optional) Plain text archives (unlike how Thunderbird does it)