Prior to RFC1123, a successful reply to the SMTP VRFY command was always prefixed with a 250, meaning that sending to this address was likely to result in successful delivery:

VRFY user
250 user@here.us.edu (Full Name)

Here, sendmail states (with the 250) that it interpreted the address as valid locally and that delivery or relaying to another site would be attempted.

RFC1123 now requires that shades of meaning be conveyed in that success code, so the correct prefix should be 252, which means that the host will accept the address and might attempt to relay it elsewhere.

If the F=q delivery agent flag is set, sendmail returns the 250 prefix; otherwise, it returns the 252 prefix. It should be set only for delivery agents doing local delivery. For configuration files earlier than version 7, the F=q delivery agent flag is automatically set for the local, prog, and *file* delivery agents.