Syntax error, not used as end of line Command out of sequence Sender OK No valid recipients specified Send your message not known User Error getting mail drop known User Forwarding to Unrecognised command bytes available) Not enough space in users account ( bytes Account limit is Users account disabled Unrecognised keyword Syntax error, no > Syntax error, no < HELO or EHLO command expected hello Message received OK bytes available for Not enough space, only bytes for Account limit is Error receiving message bytes available) Not enough space on server ( running closing connection NOOP OK This is not a mailing list Error opening mailing list Connection reset User not local User not known