Does anybody managing a #Mastodon instance have this issue too?

While reviewing our e-mail logs we found a massive (thousands per day) failed delivery attempts to the domain associated with our instance.

They are all rejected at the origin and look like an attempt of account enumeration with multiple RCPT: attempts per request.

This has always been a thing, but since Aug 21st it literally exploded (coincidentally, it's the date when we upgraded to 4.1.6).

/cc @Mastodon