We were using for the past 4 years PostMark (postmarkapp.com) to send Email to our customers.
It was done from ASP.Classic using SMTP:
port 25, 2525 or 587
It no longer works. Seems that these ports are now blocked.
We selected Postmark as we could use DKIM to avoid emails be considered as SPAM as it happened with relay-hosting.secureserver.net.
Any advice ?