.NET MailMessage and SMTPClient Getting Tagged as Spam


I'm preparing basic HTML email and have used a basic HTML template with proper HEAD and BODY tags, but for some reason, my users are having trouble getting emails from me.

I'm using ASP.NET MailMessage and SMTPClient objects and the mail sends just fine, I can get test messages to myself and most users are getting them, but some sites are flagging my messages as spam.

I'm sending them one at a time too, not multiple recipients etc.

When I send a message from Thunderbird to the same mail server and through the same account, all is fine. But the ones I prepare via the web are getting tagged by some as junk.

I checked with my host and corrected the mailserver to "Localhost" (that's how the webserver sees the mail server) and that cleared up some.

Is there anything I can do or should be doing to make sure the messages come through loud and clear? Flags, attributes, etc?


Best Solution

From address will help. Once you're marked as spam (the server that is) it's a non-programming related task to unmark. I.e. the mail servers remember!