Patrick Giagnocavo wrote:
This DID actually bite my company about 3 years ago.
A customer went to China (usually in NYC) and could not send email
through the mail server because they were using POP-before-SMTP instead
of the mail submission port .
The problem did not lie with blocking IPs. But with offering a flawed
service such as pop before smtp to begin with. I know many ISPs/ESPs
still do, much to my chagrin. The only way to submit email should be
port 587 with TLS encryption, 3 years ago one could be forgiven for
offering deprecated (*) port 465 with SSL, but not anymore (msoft
clients have been fixed).
Regards,
Jeroen
http://www.iana.org/assignments/port-numbers
* urd 465/tcp URL Rendesvous Directory for SSM
