Re: Does not compute!
He probably uses it because:
1) Volume - The quantity of general mail he gets and the amount of spam he might get be vast, so he needs something that can handle the GBs of email smoothly. His inbox size could be huge and difficult to not only maintain but search. Bet he doesn't "Inbox Zero" at the end of the day.
2) Conversation View - Yes I know that Thunderbird or other tools do provide conversation view but Thunderbird is increasingly less performant especially on larger mail boxes (in my experience).
3) Spam - This is the controversial part of the mix because it is the bit that failed, but good spam filters are rare.
I spent many years running my own mail server, dealing with spam filters, I've moved to a hosted solution mainly because I can't be bothered with the hassle any more. My IMAP host isn't google which means it is relatively slow and has terrible webmail, but at least I don't have to worry anymore.
Anyone have any suggestions of good value hosted IMAP providers with decent webmail (e.g. Horde IMP not just Squirrel Mail) and configurable spam filters?