550 5.1.0 sender rejected

[TedS]

I am a simple User of email through Shaw.ca. My friend is a User of gmail. He sent an email to multiple recipients (a bulk email?). All of the recipients with Shaw.ca email address caused this rejection message to be sent back to my friend, the sender: "The response from the remote server was: 550 5.1.0 sender rejected AUP#BL". I have had numerous "Chats" with the Shaw.ca people, checking all of my Settings; my friend the sender has had numerous Chats with the gmail people. Both sides say the problem lies with the other email provider. Now my friend the sender receives the rejection message every time he sends a single-recipient email to any Shaw.ca user. How can I have this situation resolved so that I (and all Shaw.ca users) can receive emails from my friend, the gmail user/sender.

[Dustin Anderson · Accepted solution]

The destination email server that generated the 5.1.0 error won't accept messages from you (the sender) or messages for the recipient. This can happen if messages from you (your email address, your Exchange Online organization, or even all of Exchange Online) are being blocked by the recipient.

Basically, Shaw.ca rejected it, and only they could tell you why.

[TedS]

Thank you! Your explanation supports what I have been trying to tell (in my not-so-technical terms) the Shaw 'Specialists' in several Chats over several days. I Chatted one more time and gave the Specialist your explanation, and it put my issue up a level in their Troubleshooting system. Hopefully I will have this resolved in "2-3 business days" - which is an unacceptable time frame, but I will take what I can get. I won't be recommending the Shaw.ca Troubleshooting system to anyone.

[Dustin Anderson · Accepted solution]

Yeah, I run the system at our company and there are so many settings that could be the trigger, but more than likely a block as possible spam, to them just not accepting gmail.com. I can probably guarantee it's not a SPF/DMARC failure as that would be a bigger issue for gmail.

Realistically if the know the from and when, they should be able to find it in logs and get the error. Not sure how big they are, but some companies have horrible tech support due to tiers.