I'm using TCPware to expose VMSMail through an IMAP interface and SMTP forwarding through TCPware to an SMTP server (MDaemon) on my XP box.
Why via your XP box?
My PWS Alpha is routed directly onto the Internet, and my ISP forwards all mail for my domain directly to it. The VMS mailboxes can be accessed via the web using YAHMAIL - not very fancy, but quite basic stuff so VERY well suitable for dial-up and bad lines - and by POP to read it to Outlook on my PC's. The machine is set up as a relay to send mail from the PC's out to the whole world, and will accept mail for my domain only (ISP tests reguraly

and never succeeds, of course

)
On another machine (DEC3000...), I'm testing CommunigatePro (commercial software), that can well be used as a web-replacement for outlook. That uses RPOP (or IMAP, or whatever) to read my normal mail plus a number of external mailboxes.
Good stuff, by the way, very efficient but the web interface is more elaborate and requires more processor and disk access and bandwidth, and the DEC3000 is a bit slow on that.