Automated email sending system - Spam Weight

Good day,

We have developed a system that send out automated mails to our clients, with a pdf attachment. Some of the clients have mentioned that the mails are being picked up as spam, and the IT guys say that the mails have a high spam confidence

As mentioned the headers from your system include a 2.0 TotalSpamWeight, while it should be < 0.

What should I be looking at to change this?

I am using Delphi 2010, indy 10's tidSMtp c开发者_开发百科omponent to make the mails. The body is in html, and the images in the body are externally hosted.

Please advise

Ask the IT guys which rules are being triggered.

This might not be Delphi-related. Is the sender of the email from the same domain that sends the email? You could ask your client to send you the headers of the message that they received as spam, then examine those headers. The TotalSpamWeight is calculated by some anti-spamtool, possibly from SmarterTools or SpamAssassin and might just be related by some keywords in your email. The word "Viagra", for example, would trigger a lot of anti-spam filters, even if you mention it in such an innocent way as I just did...
Oh, those externally linked images could be what triggers them! Many spammers use them to track emails and tend to add a special code to each image which would confirm if someone's email address is real or not. If the image is downloaded, they've confirmed the email address. If not... Well, this trick is why external images would trigger emails as spam. Especially when combined with some other keywords.

There are a lot of factors typically used to determine 'spam weight' and they vary from system to system. It's hard to say without knowing which system is doing the grading and the factors which the system uses, and an example message.

However, the easiest thing to look for a developer to examine is message validity.. if you have a HTML message - is it constructed correctly? Is there a plain-text alternative message part? Is the content-type correct? Having a poorly constructed message can usually add spam weight.

Also look for likely flags such as embedded javascript within your message content...which I'd assume is an universal spam weight trigger. HTML emails typically should be constructued with plain old HTML without a lot of bells and whistles.

One approach to always take when developing emails is to send yourself a message to different systems like GMail, Yahoo, HotMail.. and look at the message headers yourself. There are typically some clues left inside the message headers to help you determine why it was flagged as possible spam.

There are ways, typically outside of the developer's control, on how to reduce spam weight as well that you should be aware of... SPF records likely being the most common quick add that your IT guys should be doing, then there are Domain Keys, white lists and a host of 3rd parties willing to take your money to help validate your messages.

Good luck!

What I would do: install a Spam filter in my computer network and send the mails to myself. Then I could easily check the filter log files or other information sources of the filter. With some documentation of the filter software, it should be easy to find the cause of the spam alert.

Maybe there are even online services which can be used to test a mail with one ore more popular spam filter systems, just like online virus scanners.