Mail runs slow with IMAP Gmail. Inbox too big?

Hello everyone,

I am a journalist who deals with a large volume of emails. Until recently I had been using Mac Mail to access my Gmail account through POP. However, I recently re-added the Gmail account in Mail as IMAP, so that read emails would be synced with my iPod Touch.

Since the switch to IMAP, I have noticed Mail running much more slowly. It takes longer to send and receive messages, and it takes longer to search for messages. The inbox folder has that swirly icon beside it, suggesting that it is constantly updating. I have even noticed a reduction in speed in other web applications such as Safari, although I cannot be sure that is related.

I have followed the usual instructions to make IMAP Gmail most compatible with Mail, e.g. https://support.google.com/mail/answer/78892?hl=en

I am now wondering whether, in switching to IMAP, I should have made more of an effort to clean up/organize my inbox. I have rarely bothered to sort and delete incoming mail, because the search option worked so well and because there was no speed issue. But now I am not so sure.

I have about 18,000 emails in my actual inbox. A further 50,000 or so are in various folders under the ">ON MY MAC" section; these arrive here automatically through various Rules I have set up under Mail preferences.

Is there anything I can do to make Mail run faster?

For example, should I go through my inbox and either delete or put into folders most of the messages? (That would be an enormous task!) Or should I be sorting messages into the folders in the ">GMAIL" section (as opposed to the ">ON MY MAC" section)?

Part of the problem, I suspect, is that I don't really understand how IMAP works. Is it constantly looking for updates (e.g. read/not read, flagged/not flagged) for all of the 18,000 emails in my inbox and 50,000 emails in my ">ON MY MAC" folders?

Any help would be most welcome!

Best wishes,

Jon