Mail filters

From Wikanual

INTERDUBS sends email. It always does. If it can not send the email out you would see an error message and we would get a notification.

The same would be true if the email can not be delivered to the mail system on the receiving end. Sometimes there is a little delay in those errors since mail systems will try to redeliver a message should the receiving system not be available. This is not the case here (or in general nowadays) either.

But still sometimes emails will not reach the recipient. The cause are so called 'spam filters'. They try to filter unsolicited mail. There are two types of these filters:

Mail software itself like Entourage or Apple Mail do this and often put these spam mail into seperate folders from the inbox.

And often companies use filter systems on as part of their mail infrastructure. This can be done in-house or as a service that you can subscribe too.

All these filters work in the same way:

They look at the email and look for specific patterns. Each match of those patterns goes into a total score with specific weights. Different systems are different in their evaluation. On top of that there are 'learning filters' that will dynamically update their criteria.