Mail memory usage?

Solution 1:

First i would try and isolate the problem. Is Mail.app taking the same amount of memory on a new user account, im talking about a OS user account (Create a new test user in System preferences -> Users and Groups -> +)

In case it does i would look at "/Library/Application Support/Apple/Mail" and compare to a known good system (which only should contain Stationery) im suspecting you might have some plugins that make Mail.app use more memory than usual (i have 21k mail in my inboxes and it only uses 230mb).

If only your exciting user show this behavior, start by moving the ~/Library/Mail folder to like ~/Library/Mail.old and see if it stops using ram. Otherwise i would start looking for plugins or other applications that may interact with mail (there might be some internet plugins)