Question

I’m implementing a email newsletter sender service using .NET and Windows Server technologies. Are there comprehensive guidelines which could help avoiding emails being trapped by spam filters and other mechanisms?

They should cover all aspects of (legal) bulk mail sending: SMTP configuration, DNS, HTML content, images, links within content etc. A simple example: is it better to embed images or load them from a server?

It would be great if you could provide some empirical data to show the efficiency of some measures taken.

Answer 1

Although I don’t have a definitive answer, I think this is a very important question. Here are few tidbits I know about it

1. Choose a clean hosting/smtp server. IP addresses of spamming SMTP servers are often black-listed by other ISPs.
2. Send a simple introductory email to every subscriber, asking them to add your sender address to their safe list.
3. Be very prudent in sending to only those people who are actually expecting it. You wouldn’t want pattern recognizers of spam filters learning the smell of your content.
4. If you don’t know your smtp servers in advance, its a good practice to provide configuration options in your application for controlling batch sizes and delay between batches. Some servers don’t like large batches or continuous activity.