Hello, 

I have problem with configuring SMTP for magento site. I am keep getting error like this in my inbox. 

INVALID_ADDRESS, ERROR_CODE :550, ERROR_CODE :5.1.1   : Recipient address rejected: User unknown in virtual alias table. 

I was thinking that is problem due to SMTP configuration. But when I try to logging in with Mozilla Thunderdbird I constantly getting that my Username or password is wrong. I triple checked all config. My MX record is verifed also.

Greetings