[kwhitefoot]

I have a rule in Thunderbird that puts all email that comes from senders not in my contacts in a special folder.

[neilv]

Same here. For simplicity, incoming emails from senders that aren't in my addressbook go automatically to the "Junk" IMAP folder, together with what the email hoster's spam filter moved there.

That rule has a few exclusions. For example, incoming emails from a handful of particular universities and companies I work with can go to "Inbox" because seeing them ASAP is likely important.

[lupire]

What happens when you ask someone to email you, but you don't send them an email first?

[neilv]

Then I might not see their message for a day or so, unless I'm actively checking more frequently for it, or unless I add them to my addressbook ahead of time.

[kwhitefoot]

That's why my rule doesn't put it in the junk folder. I put it in a sub-folder of the inbox so that it is easily seen.