Todays idiot mail server of the week award goes to webcontrolcenter.com!
All seems to go fine, until you try to send email as postmaster:
[~] edwin@k7>telnet mail22.webcontrolcenter.com 25 Trying 188.8.131.52... Connected to mail22.webcontrolcenter.com. Escape character is '^]'. 220 mail22.webcontrolcenter.com ehlo edwin.adsl.barnet.com.au 250-MAIL22 Hello [184.108.40.206] 250-SIZE 31457280 250-AUTH LOGIN CRAM-MD5 250 OK mail from:<> 250 OK <> Sender ok rset 250 OK mail from:<email@example.com> 250 OK <firstname.lastname@example.org> Sender ok rset 250 OK mail from:<email@example.com> 550 Sender is not allowed. Connection closed by foreign host.
And they rudely close the TCP session for you too!