Hi All, I’m getting complaints from Customers that their reply emails are bounced with a message 550 5. 7.1 relaying denied. Anyone knows how to fix this issue. I tried myself on personal email . I got one reply bouncing out of another 5 replies. Any help is appreciated?

that article already answered you.

True for outbound emails but not for inbound replies!

if there's a FiredEmployee@company.com which the account has been disabled, emails going to FiredEmployee@company.com get NDR

All active accounts for users

outbound, then it's probably system issue. open a case.

It’s the replies from customers