Backup your Google Apps (or Gmail) e-mail over IMAP using imapsync

I have confidence in Google's ability to keep their e-mail service up-and- running and keep proper backups of data, but my e-mail history is my data and I like to have my own copy of it. Since Google provides access to your Google Apps (and Gmail) e-mail over IMAP, you can do all kinds of things using standard tools, e.g. synchronize your Gmail e-mail to a local mailbox using IMAP.

I run an Ubuntu box at home and it was easy to install the dovecot-imapd package to get an IMAP server installed. Since my box is behind my router/firewall, I'm wasn't that concerned with tweaking Dovecot's default configuration, but I'm sure you could fiddle with the config to ensure that Dovecot only binds to 127.0.0.1.

From there, it's just a matter of using imapsync, just like I ended-up using previously to initially transfer all my e-mail to my Google Apps account.

Here's the script:

# Sync e-mail from "username@yourdomain.com" to localhost, using IMAP
imapsync --host1 imap.gmail.com --user1 username@yourdomain.com
         --passfile1 /path/to/gmail_mirror.passfile1 \
         --host2 localhost --user2 username
         --passfile2 /path/to/gmail_mirror.passfile2 \
         --ssl1 \
         --useheader 'Message-Id' --skipsize --allowsizemismatch \
         --syncinternaldates --noauthmd5 -nofoldersizes\
         --split1 100 --split2 100 \
         --regextrans2 's/\[Gmail\]/username\@somedomain/' \
         --include "All Mail|Sent Mail" --delete2 --expunge2

The --regextrans2 option rewrites IMAP folder-names on-the-fly, so that my local IMAP folder structure can be different than the structure on Gmail's server. For example, the top Gmail IMAP folder is [Gmail] which wasn't all that useful for me, so instead I rewrote that top-level folder to be username@somedomain so that the local folder name (e.g. in ~/mail/) would match the source e-mail address.

You can also use the --include option to decide which IMAP folders to copy. I opted to just copy "All Mail" and "Sent Mail", which gives me a copy of all my mail but doesn't preserve any information about the labels I might have had assigned to those messages in Gmail.

The initial copy will definitely take a few hours (or more), depending on how much e-mail you have in your Gmail account. But this works great for me and stores the mail in "mbox" format locally so I can even access the mail locally via mutt/alpine/etc.