I recently found out about two-factor authentication (I’ve seen this abbreviated as 2FA) on my Google Mail account. Wanting to get with the security program, so to speak, I dutifully set mine up. If you’re interested in doing the same, here’s a useful primer on how it works.
For each application you use that doesn’t support 2FA directly, you need to set up an individual authentication code which is different than your Google account password. You are able to manage each of these separately, including removing access for a specific app if needed in the future. So you would set up one code for your Evolution email client, another for offlineimap, and so on.
However, I made a boo-boo and forgot to set up an authcode for my local mail server, so a few days of my outgoing Gmail has been backing up. (So yeah, I need to set up proper deferral notices so I’ll notice these types of problems sooner.) I just fixed the problem, so if you see email from me that’s a couple days old and out of sync with the conversation, you’ll know why.