550 5.1.1 RESOLVER.ADR.RecipNotFound
One of my coworkers reported that whenever he sends an email to a new vendor he gets an undeliverable stating "The e-mail address you entered couldn't be found..." listing the error in the subject line. Everything works from his personal Gmail account.
He forwarded me an email from his Gmail account. I clicked on the vendor's email address in that email and sent an email to hm. I also received the undeliverable. I have also typed in the email address and gone to their website an clicked on the email address on the site and got the same result.
To make matters more confusing, I sent him an email from my home Comast account and he received it. However, he replied and I never received it nor is it in my Spam folder.
I've seen references to this being an issue with the Contact or an auto-complete entry being corrupted. This email is not in my Contacts nor does it auto-complete when I start typing. I've seen references to this online.