.NET MailMessage and SMTPClient Getting Tagged as Spam?

Question

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?

TIA!

Answer 1

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!

Answer 2

One thing you can do which I've just learned is to update your DNS with some domain keys to verify that the domain in your from address is valid.

http://en.wikipedia.org/wiki/DomainKeys_Identified_Mail

Answer 3

Are you using a shared hosting? If so some other site in your server may be sending out large emails (may be genuine) so some servres migth have marked the server as SPAM.

There is nothing you can do programtically to the tell the server that you are not spam. You are already doing what you can i.e not sending too many messages at a time.

If the mailing list is not too long then you can sendout a personal email to everyone saying that some users have reported not getting the emails so it is better for them to check SPAM folder and mark the email as "Not spam" to receive future emails.