Furthermore, you have to jump through several difficult-to-recognize hoops to get that 9GB on your disk. IMAP will only sync what the sever feels are recent emails, and envelope information for the rest.
Depends on your email client. Thunderbird downloaded full copies of two of my Gmail accounts when I added them and selected the "Keep messages for this account on this computer" option.
OfflineIMAP crashes a lot. I have been using it for many years and with each upgrade, I'm optimistic that stability and/or performance will improve, but it still sucks a huge amount of CPU and hangs several times per day.
See also: https://github.com/rgrove/larch - "Larch is a tool to copy messages from one IMAP server to another quickly and safely. It’s smart enough not to copy messages that already exist on the destination and robust enough to deal with interruptions caused by flaky connections or misbehaving servers."
