Ubuntu :: Recommendation For Simple Email Client?

I am looking for an email client with the following specifications. I have trialled most of the commonly recommended clients but have found ongoing irritations that push me to keep looking.

Specifications

1. specific email client, not PIM
2. can run as a portable application or configuration files and mail can be stored remotely
3. minimal or no dependences
4. can scan for viruses

[code]...

Evolution matches 5, 6 and 9. The program is a good general client but slow and glitchy. Can't scan for viruses in emails. Kmail matches 1, 4, 5, 6, 7 and 9. Does most of what I need with the powertools plugin but does not play well with Gnome. The program comes with too many dependencies that makes it very hard to move data around or even use on various machines. The dependence on the akonadi server is quite frustrating and makes this kde application a great product but only really useful on kde. Thunderbird matches 1, 2, 5, 8 and 9. Again reasonably comprehensive but lacks the basic ability to scan incoming emails (filters can pipe incoming data to an external program). The fact that the mail is intrinsically linked with your Mozilla profile makes working with the email file very difficult.

Clawsmail matches 1, 2 (old version), 3, 4, 5, 6, 8 (Windows Port old and not maintained) and 9. Looks good but appears to lack portability and a current windows version. I want to check my mail (predominantly POP accounts), have spam and viruses set aside/deleted/quarantined, have my attachments saved to a directory so my mailbox does not get too big and for the emails and configuration data be stored in a distinct directory that can be readily synchronized between computers. The program should be able to run on Ubuntu and Windows XP/Vista/7, on the same data once the data directories are synchronized. And no, I don't want an Internet based option like gmail or yahoo.