Matthew Bloch is one of the key team behind Bytemark and he has posted about what he sees as a lack of progress in the development of email as a technology.
I am one of those who wanted customisation of their mail handling, my family has followed me and is using my host because the majority of mail hosting companies couldn't account for connection oddities. I use MailWatch to track MailScanner filtering quickly and tweaking the filtering has been very important. I have one domain of mine hosted with Google Apps just because I can and it is good but perhaps it lacks the granularity for heavy business use?
If a mail hosting company was able to provide the same granularity of control as MailScanner + Postfix + PostfixAdmin + Mailwatch + MySQL + Dovecot1.2 then I think it would give businesses a case to drop their internally hosted servers. Adding RequestTracker into that mix would just be the final leap to give them a feature not available with most off-the-shelf systems.
On the mail client side what I have come to realise is that I can't navigate my email quickly enough. I have many GB of email and at work I have thousands of emails waiting to be sorted into the myriad of sub-folders. I think the answer is tagging and bayes suggestions but I think tagging hasn't truly been leveraged to it's maximum. I think it should be possible to browse tags with depth to narrow down the emails. Thus the initial view should have every mail, there should be a tree list of every tag; then each tag should have every tag which is shared with the previous tag. Thus a matrix hierarchy of tags can evolve and with Bayes suggestions mails can be tagged as they arrive (I already use the Bayes sort add-in for Thunderbird). In this way the mass of mail can be filtered down to the target quickly and more importantly mail can be in many places! An email might be to do with marketing but also to do with a client.
Perhaps I need to blog this....
Anyway, good posting!
I've been thinking about this concept for a matrix mail client for some time and I think I need to write a white paper about it so that I can see if I can drum up interest in developing it! I will see what I can do.