Shrink e-mail? Sync POP3 mail?

I'm an avid user of Thunderbird, but I don't like using PTB because the e-mail files get so big (I only have a 256M drive, and I'm approaching 1GB on my desktop), and because I have no way to synchronize my e-mail.

Regarding e-mail size: Since it's all plain text anyway, if I compress it with 7z it really shrinks down -- but I can't do this for PTB reliably. Would anyone have any ideas? I'm thinking an NSIS script with 7-zip that keeps PTB in a 7z file, extracting/compressing as needed to use it (there's 50+ GB on these comps, so keeping something on the desktop a few minutes isn't a problem).

Since I use GMail, I have POP3 access, but no IMAP (as of yet :(). Is there some way I can synchronize the two profiles reliably? I'd use Profile Sync, but my Mail folder is in D:\AppData\Mail and my TB profile is in %appdata% (my primary partition is tiny). I don't use the two simultaneously, so I don't have to worry about comparing e-mails.

Thanks for any thoughts.

~nm35