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
MAILER-DAEMON@mail-fwd02.dca.untd.com
11:48 PM (6 minutes ago)
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?
Thank you!
MAILER-DAEMON@mail-fwd02.dca.untd.com
11:48 PM (6 minutes ago)
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?
Thank you!