Originally Posted by PantieZ

hmmmm ....

This is the Postfix program at host localhost.localdomain.

I'm sorry to have to inform you that your message could not be
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The Postfix program

<*****@optonline.net>: host mx1.optonline.net[167.206.4.77] said: 550 5.7.1
invalid greeting 207.150.184.225
<URL:http://www.optonline.net/mailblocking>: *****@optonline.net (in reply
to RCPT TO command)