Dear Email Admins: How widespread is the use of RFC 5233 Sieve Email Filtering, that is, the acceptance of user+foo@example.com and user+bar@example.com both being delivered to user@domain.com?

For a lowish traffic application, would it be reasonable to tell people to do it, and then just deal with exceptions as they come up? We’re probably talking a few dozen users total.

EDIT: Do we have any actual stats? I mean once we have Microsoft, Apple, Gmail etc in there, who’s left? Just weirdos and cranks and Linux users. ;)

@stilgherrian Are you interested in actual sieve email filtering support, or just plus addressing in general?

@jamesh Well spotted. Just plus-addressing in general. It doesn’t need to do the sorting into sub-boxes.

@stilgherrian It's probably simplest to ask the user to try and email themselves via a plus address and see if it delivers or results in a bounce.

With how centralised email is these days, I suspect the vast majority of people have access to plus addressing. Sieve filter language support is probably fairly spotty. You definitely won't have it with Gmail, Outlook or iCloud email.

@Tubsta @stilgherrian

It should work, but it might not for old indie sysadmins still running ancient sendmail etc