This seems to pop up only when I send an email from my gmail account to one particular person, who has a Juno email address. The email gets through but I get a response saying
to me Unfortunately, your mail was not delivered to the following address:
<xxxxxxx@hotmail.com>:
Connected to xxx.xx.xx.xx but sender was rejected.
Remote host said: 550 5.7.1 Unfortunately, messages from [xx.xxx.xx.xx] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to Troubleshooting. [CO1NAM05FT031.eop-nam05.prod.protection.outlook.com]
It's not the end of the world since the emails get through, but it's annoying. Any ideas?
It appears your Juno contact may have automatic email forwarding enabled. If the issue is only with that contact, I'd send a note letting them know to check the email forwarding & filters settings on their end.