> I’ve run a fair amount of email campaigns where we strip out the + if gmail is the domain to ensure it doesn’t end up in some weird filter.

At which point you should wind up in the "how widely can I advertise that you're a spammer and all your outbound email should all be routed straight to /dev/null for sending mail to an email address you were never given" filter.

I think that marking the mail as spam sends a signal to their email provider, putting a mark on their account?

Depends on your isp and which email provider they use. The big marketing email services generally do have the feedback loop setup with Gmail though, so yes, you are right.

> I’ve run a fair amount of email campaigns where we strip out the + if gmail is the domain to ensure it doesn’t end up in some weird filter.

Which works, until the Gmail users who bother using + addresses with filters start giving all legitimate senders + addresses and sending everything thst doesn't have one and doesn't come from Google straight to deletion (possibly with a stop by “mark as spam” en route.)

The problem is not all legitimate sites/sources will actually accept '+' as a valid email character even though the RFC says it's a valid email character.

Jinx. :D

Yeah problem with that is the number of crappy regexps sites use that stop you from signing up with a + address in the first place.

Sounds like a great way to get your email marked as spam.

I wonder if it could be argued that this violates anti-spam regulations. Depends on how “plus” addresses get interpreted. Are they a different recipient?