I'm a heavy user of Spamcop's Webmail system (to the exclusion of any other MUA, web or Windows-based). I love the convenience of web mail with a sophisticated folders/filters/Popgating.

See this link for the IMP Roadmap

I noticed that Spamcop uses IMP 4.1.4. IMP 4.3 has been out since Sep 2008 and IMP 5.0 is planned for later this year.

Features added from 4.1.4 -> 4.3 that I'd love to have:

• auto-complete address lookup
• per-folder sort preferences
• remembering recent search queries
• allowing multiple browser windows/tabs

IMP 5.0 will add the following features that would be nice:

• Message highlighting/flagging (improved with custom tags)
• improved search gui

Are there any plans to move to newer versions of IMP anytime soon? Based on the integration of Held Email and spam Reporting, I'm guessing there is customization work that Spamcop has to do before any upgrades are possible.

Not speaking for SpamCop but am just going to note that when SpamCop last upgraded to 4.x, it was upgraded from v2.5.x. Updates to v3 ran into major issues.