Optimum SMTP rejecting one account's "sent" email as spam
Hello, The Optimum SMTP is recently rejecting emails I am sending from one of three Optimum email accounts that I have. When using the one account I get the following rejection notice:
Sending of the message failed. An error occurred while sending mail. The mail server responded: Spam detected by content scanner. Message rejected (ID 6661A65F0037E564). Please check the message and try again.
This only occurs when I use Thunderbird to send messages. If I use Outlook on the same computer, I do not get the error. Previously, I was getting the error on all three accounts, but when I upgraded to 64-bit Thunderbird, the problem went away. Of course, I called Optimum and they said that the problem was on my side and were not helpful. They also don't take any responsibility if you don't use their web interface.
I would appreciate any ideas that anyone has on what I could try to eliminate this problem. Thank you.
All Replies (1)
Remove your signature and try to send.
Email signatures are a common cause of false positives in outgoing spam detection tools used by providers that rarely actually understand email at all. Hence their reliance on the web portal someone else maintains for them.
At a specific level it is often the images used for social media (Facebook, X etc) that have been used in spam and are now in your signature than are the cause, but the general remove your signature is a good starting point.
Another specific is using a signature generated in Microsoft Word. It sounds innocuous, but the paste from Word brings hundred of thousands of useless characters with it that includes items that can actually be used in spam. Essentially the same template data is send from word every time, even if it is hidden from view it is in the email and can form part of the spam signature used by the detection software.