> I've been doing some tests of my postfix server and sometimes when I > connect, I get *two* ESMTP banners, one that has a hyphen (-) after the > 220, and one that doesn't. Other connections, I only get one banner: > > $ nc -v server.example.net 25 > Connection to server.example.net (10.0.0.1) 25 port [tcp/smtp] succeeded! > 220-server.example.net ESMTP (spam is not appreciated) > 220 server.example.net ESMTP (spam is not appreciated) > quit > 221 2.0.0 Bye > root@mon02-mtl:~# nc -v server.example.net 25 > Connection to server.example.net (10.0.0.1) 25 port [tcp/smtp] succeeded! > 220 server.example.net ESMTP (spam is not appreciated) > quit > 221 2.0.0 Bye > > Can someone explain what the two banners mean, and why they happen > sometimes, and are slightly different?
220- (with hyphen) means that the server has not finished sending yet. Often this is used to detect spammers that don't play by the rules and send smtp commands without waiting for answers (pipelining). e.g. http://www.postfix.org/postconf.5.html#reject_unauth_pipelining Or if an answer is too long and is broken into several lines, all lines but the last will have a hyphen after the status code. Best regards Gerald
