PHP contact form giving 550 5.1.1, “User unknown”
Hi, I run an Ubuntu server with Apache2. I have a PHP contact form in domain1.com. The contact form is configured to send messages using SendMail to email@example.com (domain2.com is a Zoho hosted email).
A few hours ago I was being able to send messages via contact form, but it suddenly stopped to work and started returning this error:
firstname.lastname@example.org… User unknown
These answers are provided by our Community. If you find them useful, show some love by clicking the heart. If you run into issues leave a comment, or add your own answer to help others.×