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I had no idea this was possible. This sounds almost like an HTTP OPTION request. I'd love to find an example of client code which does this.
by ethagnawl 1y ago
I had no idea this was possible. This sounds almost like an HTTP OPTION request. I'd love to find an example of client code which does this.
- brk 1y agoYou're looking for the SMTP VRFY and EXPN commands. However implementation is very hit-or-miss. In the good ole' days of the internet, VRFY was widely implemented. Then spammers realized they could connect to a mailserver and do a form of a VRFY dictionary attack to find valid addresses, so it stopped being supported.