Like you, I have been contemplating what to do about the mail in the future. I recently opened a trial account at Rackspace to try them out once again. And once again I was reminded that many functions that I need are not available there. Besides spam digest/report they don’t have the option to adjust the “aggressiveness” of the spam filter, and they don’t offer domain aliasing for accounts (so adding more domains for the same accounts costs extra). The aliasing arrangement I’m currently using would become a lot more expensive were I to move to Rackspace.

As it stands, it seems the only way to get the mail working well is to bring it in house. I like Postfix+Dovecot, and there are many external spam filtering services to choose from (I should actually write a review of them..). Spam filtering in-house is often more trouble than it’s worth considering easily the large volume of spam as well as the effort to keep the filters accurate. An arrangement where the email is received by a filtering service (which would provide filter adjustments, a web-interface to manage/search spam, spam reports, and valid mail caching) with an internal mail server that would only receive non-authenticated mail from the spam filtering service’s forwarders would likely work the best. With valid mail caching, and possible web-interface to the cached mailbox would also remove the stress of having to ensure that the internal mail server never fails; in such event those features would make sure that no mail is lost and that there is temporary access to it while the internal mail server is recovered from a failure.

Fusemail is good for businesses that do not rely on email…

For external service I’d compare Fusemail and Rackspace, though there are many others like BlueTie. Google’s hosted service I find somewhat scary because it is notoriously difficult to get hold of anyone at Google if problems arise.

However, I’ve continued to use Fusemail for my internal mail (five human users plus few generic accounts) since then. It has worked reasonably well: there have been no major outages or other significant issues with the service. The only gripe I currently have about Fusemail is that their IMAP has some issue with Outlook 2010 (or Outlook 2010′s IMAP is somehow broken — I haven’t tested it with other IMAP services yet). When deleting messages from an IMAP folder the message IDs get out of sync and Outlook starts complaining.

For this reason I have recently considered retrying Rackspace Mail (when I last tried them out they were lacking many features I really needed and that Fusemail offers), or caching the mail locally with Postfix – an arrangement that worked very well with small extra management overhead. Since the local cache is really just a duplicate of the remote mailbox it’s also not critical for operations. If the local cache server should go down, users can continue to access mail at the mail provider server without interruption.

A cache on the LAN would obviously remove any lag that might result from use of a remote service, and there would be full control over the [IMAP] interface to the mailboxes.