I have my ananzi email account, 2 gmail accounts, 1 website domain email account.
I forward my ananzi > domain. Then I let gmail pop3 into the domain account and archive all those emails and then also let it pop3 into my other gmail account. All my mails in one place.
I should now just set up IMAP and keep a backup copy of my main gmail account on my PC for in-case...
We're using EAS for Exchange mail archiving. I find it a little odd in many ways (man, you really need the training course to understand it), but it does the job well. The local suppliers, Soarsoft, are very helpful.
Using Linux for hosting my own e-mails. Archiving is a breeze, I just procmail all my e-mails and copy each and every mail (after the spam process) to a Archive folder that gets compressed at day end