Many companies and organizations use SPAM filters to block unwanted email. Called SPAM, or UCE (unsolicited commercial email), it is a huge time drain for everyone to delete all of the junk that shows up on a daily basis. We feel for you.
Tendenci has an electronic newsletter functionality built in. The newsletter generator builds the newsletter with your branding based on content added by your users. If you are an organization, ideally no more than 10 to 15% of the content on your site is "created" by the administrators or webmasters.
What this means is you don't have control over the subject lines used in calendar events, articles, press releases, directories, etc, that are added by your user base. This can cause spam filters to mark your electronic newsletter as SPAM based on certain phrases or words. Things like "accept credit cards" or "viagra" are surefire ways of telling the spam filters that you are spam (surely this content would be flagged as well!).
The "once for all time for all users" solution to this is to have the recipients mark your sending address as not-spam. Or to whitelist the IP block of your web site -- meaning mail servers of your recipients will accept any email from you. This is something the recipient's network administrator must do. You can't control it.
So if a user says "your newsletter is showing up as spam" you have two options.
- Evaluate your content for spamminess and rewrite it, then test again. I don't recommend this option, but feel free to try.
- link them to this page and say "please forward this to your network admin to whitelist our site for email".
For more on SPAM, and again we recommend you do NOT attack the issue as many before you have tried with no success, but if you must, read more here: