IMAP GMAIL DOWNLOADING THOUSAND OF MAILS CONSTANTLY

Question

On my laptop, I have one gmail IMAP account set up. It is quite old and has tens of thousands of messages stored in many folders.
Mail.app is caching them locally, but frequently it seems to feel the need to re-download many thousands of them. The Mail Activity panel always shows things like "Incoming messages: 4507 of 10833, 53 KB/s".
If I look at the activity window, it is synchronizing IMAP folders ... and the folders it is synchronizing haven't changed in over two years: I have stopped storing new messages in them. So it should already be synced, and Mail.app shouldn't have to download new messages anymore. But it re-downloads them often.
I don't think the problem is with the folders on the server, It is a gmail account, which I'd assume Google configures intelligently. Though, the desktop is on all the time and Mail is always open, so maybe it does re-download them frequently but I don't notice.
It's very annoying because it pegs my processor at 100% for about 20 minutes every time it happens, which is often. Slows down the machine and heats it up enough to burn my lap in just a few minutes!
Any thoughts on how to get Mail.app to be sane about syncing local copies of remote IMAP messages? This is ridiculous.

Answer 1

MixMac05 wrote:
where in the General Preferences would I find the 'Scan e-mail content for malware and phishing?
Third checkbox in General Preferences.
And here's how you go about handling any .emlx infected files in the future:
When possibly infected e-mail files are found:
Highlight the entry in the ClamXav window's top pane that needs to be dealt with.
Right-click/Control-click on the entry. 
Select "Reveal In Finder" from the pop-up menu.
When the window opens, double-click on the file to open the message in your e-mail client application.
Read the message and if you agree that it is junk/spam/phishing then use the e-mail client's delete button to delete it (reading it is especially important when the word "Heuristics" appears in the infection name).
If you disagree and choose to retain the message, return to ClamXav and choose "Exclude From Future Scans" from the pop-up menu.
If this is a g-mail account and those messages continue to show up after you have deleted them in the above manner, you may need to log in to webmail using your browser, go to the "All Mail" folder, find the message(s) and use the delete button there to permanently delete them from the server. Then check the "Trash" folder and delete them there.
To fix the corrupted mailbox index(es), highlight each one that was corrupted and choose Rebuild from the appropriate menu.