220 myhost.test.ex ESMTP Exim x.yz Tue, 2 Mar 1999 09:44:33 +0000
550-Callback setup failed while verifying <userx@broken.example>
550-Called:   127.0.0.1
550-Sent:     MAIL FROM:<>
550-Response: 550 I'm misconfigured
550-The initial connection, or a HELO or MAIL FROM:<> command was
550-rejected. Refusing MAIL FROM:<> does not help fight spam, disregards
550-RFC requirements, and stops you from receiving standard bounce
550-messages. This host does not accept mail from domains whose servers
550-refuse bounces.
550 Sender verify failed
221 myhost.test.ex closing connection
220 myhost.test.ex ESMTP Exim x.yz Tue, 2 Mar 1999 09:44:33 +0000
250 OK
250 Accepted
221 myhost.test.ex closing connection
220 myhost.test.ex ESMTP Exim x.yz Tue, 2 Mar 1999 09:44:33 +0000
550-Callback setup failed while verifying <userx@broken.example>
550-(result of an earlier callout reused).
550-The initial connection, or a HELO or MAIL FROM:<> command was
550-rejected. Refusing MAIL FROM:<> does not help fight spam, disregards
550-RFC requirements, and stops you from receiving standard bounce
550-messages. This host does not accept mail from domains whose servers
550-refuse bounces.
550 Sender verify failed
221 myhost.test.ex closing connection

******** SERVER ********
Listening on port 1224 ... 
Connection request from [127.0.0.1]
220 Welcome
EHLO myhost.test.ex
250 Hi
MAIL FROM:<>
550 I'm misconfigured
QUIT
221 Bye
End of script
Listening on port 1224 ... 
Connection request from [127.0.0.1]
220 Welcome
EHLO myhost.test.ex
250 Hi
MAIL FROM:<userx@ok.example>
250 OK
RCPT TO:<usery@broken.example>
250 OK
QUIT
221 Bye
End of script