How can I keep Mail.app's archive from becoming too big?

Question

I'm trying to reduce my hard drive space used to prepare for a move to an SSD. I've got a wonderful application called DaisyDisk that allows me to visualize data segments on my hard drives.

I have three internal drives, and for the time being I'd just like to slim down the size of my startup disk, so I can move it to a smaller SSD.

By far the largest segment of my hard drive is a section under Macintosh HD/Users/joelglovier/library/Mail/V2/Mailboxes. This directory is over 75GB. You can see the visualization from DaisyDisk here: http://cl.ly/E7OJ

I found this directory before, when trying to slim down my hard drive, and simply deleted it's contents, then changed my settings in Mail.app to not archive attachments, thinking that would resolve the issue.

However, some months later this directory has again creeped up to a ginormous size.

Can anybody please help me understand what this directory is for, and how to permanently reduce it's size - via Mail.app settings, or whatever I need to change to stop it from becoming so huge.

Thank you!

Note: I'm on OSX Lion 10.7.3 using Mail.app ver 5.2.

EDIT: SO I dug through the files in the directory in question. There was one particular mailbox in /Library/Mail/V2/Mailboxes called "Recovered Messages (account name).mbox" which contained a very strange subdirectory structure of a single email duplicated thousands of times under different subdirectory structures. For example, there was a subdirectory in it that had /1, /2, /3, etc., and each one of those directories had /attachments and /messages. The /attachments on each had hundreds of subdirectories each containing this one same attachement from a particular email, and the /messages under each had hundreds of copies of the email all with different numerical file names. But the weird thing is ALL were from the same exact email.

Answer 1

Go ahead and delete that "recovered" folder, and there is also going to be an .OfflineCache folder that needs to be removed. Note the period at the beginning of the file name; you will either need to show invisible files or use Terminal to delete that folder.

This most often happens when an unsuitable large file is attached to a message. With GMail for example, any attachment over 20MB will be rejected. Mail sees the rejection by the mail server and tries to recover from it by sending the message again. Over time, these half-attempts to send mail stack up and start using all your drive space.

If you want a quick and easy way around the problem, remove the account in Mail's preferences, then re-add it. This will discard the offline cache for the account and free up your mangled space, at the expense of having to re-download the real messages.

And in the future, don't sent huge attachments. Use a specialized service like Dropbox instead.

Answer 2

I was having problems trying to migrate my email data when i updated to lion. i eventually gave up trying and just moved my /Library/Mail folder to my desktop and re-added all my email accounts. when i started to delete the Mail folder i realized it was 150 GB.

For the last 3 years I would notice that emails i had sent years ago were reappearing in my sent folder. Its funny that someone would mention using a specialized service to send large files, because that's exactly what i was doing. I was sharing files on my idisk. However the emails were not just limited to my idisk shares, there were also emails without attachments that would keep appearing in my sent box.

i contacted some of the people from these recurring messages and they confirmed that they had not received any duplicates. so i just shrugged it off. Little did i know this glitch was eating away at my hard drive. I had noticed that no matter what i did, my hard drive was always gradually decreasing.

i reinstalled more times than i can count, but for the past 6 years i have always synced my mail accounts with my dotmac/mobileme account. I realize now that it would have been better to re-add my mail accounts manually after a fresh install. i don't believe that would have solved everything, but it would have slowed down the rate of which my hard drive was filing up.

I see now why Apple has abandoned their mobileme platform and gave the mail app a major overhaul. Hopefully the issues are resolved now.

For me, the strategy to manage Mail is to not migrate in the data and start over regularly so I can see what syncs down from the cloud and what mail came from older Macs.