Thunderbird is just a program running on your computer facilitaing reading and writing of emails. It's not an ISP or mailbox or server etc. Thunderbird is not making any complaints - it's an email client.

If you send out emails and recipients using imap accounts or webmail mark email as spam, this notification of spam/unwanted mail gets reported back to mailbox provider who in turn sends info back to sender's email provider so sender can use the info to improve their emails in content or find out if people want o unsubscribe from getting more emails etc.

Read info at these links as they provide good explanations. https://www.spamresource.com/2022/06/delivterms-what-is-feedback-loop-fbl.html https://mailtrap.io/blog/email-feedback-loop/

I was misinformed. (Thanks, ChatGPT.)

We're stumped as to how these complaints are being generated.

AWS SES sends the email from our SES-approved address, which contains our domain name. Rackspace provides my email account. We've whitelisted our sending domain with Rackspace, and Rackspace denies they're responsible.

How are the complaints happening?

Complaints may be generated by recipients of your emails who have chosen to mark your emails as spam or the server spam filter that the recipients use have marked it as spam.

When you send emails have you included an option to unsubscribe from receiving mail from you ? So you get informed and can update who gets sent emails.

You may want to see if your domain or email address or IP address etc is on a blacklist. Try this link to check:

• https://check.spamhaus.org/

I'm the only recipient. (And I haven't complained. ;))

The messages are sent to me from my AWS instance. And, somehow, my email address is ending up on my own suppression list.