microsoft 365 outlook email stops sending messages

[jsainas]

On several occassions now my outlook personal email account just stops sending messages.  It receives emails OK.  They emails stall in the outbox.  I have one other account that continues to work.  Both my webmail and cel phone accounts continue to send messages.  I fixed it once be deleting the account and adding it again.  It worked for a week and stopped again.     I get the following error message, which seems to indicate the some filter is blocking the email.  Is there a solution to this?  Thank you    

Task  - Sending' reported error (0x800CCC67) : '  The server responded: 421 shw-obgw-4003a.ext.cloudfilter.net cmsmtp 108.63.251.34 blocked. AUP#DNS'

[ET12]

I am getting the same message, except mine happens only when my computer and phone are connected in a particular new location (served by Telus). At other Telus locations, or Shaw locations, they continue to work fine. I spoke to Telus and they said that account had no security issues and that my new IP address should not be blocked, but then Shaw tells me that the error messages actually originate from Telus, not from Shaw. So I am going to speak with Telus again. 

There is another thread related to this:  https://support.shaw.ca/t5/internet-discussions/shaw-cloudfilter-blocking-ip-when-using-a-3rd-party-...

I hope there is a solution.

[ET12]

To follow up, I spoke to Telus and they "released and renewed" my new IP address. That solved the problem immediately.

[Quack]

I am having the same problem this morning and have no idea why.  I don't know what to do.  So far it's on my laptop on wifi at home. I haven't tried it on my desktop yet.