Tag Archives: hMailServer

Fix hMailServer 550 Invalid HELO string error

On a web server I’m running hMailServer to handle all e-mail traffic, especially SMTP. Today I noticed in some cases the e-mail hMailServer sent was rejected by the receiving party. It turned out the receiving party was a Microsoft Exchange environment. The hMailServer SMTP log stated the following:

On the internet I found this topic. The solution to this problem is as follows: in the hMailServer administrator go to Settings > Protocols > SMTP > E-Mail Delivery tab. Enter the host name of your web server (e.g. a domain name) in the “local host name” field, and save the changes. Now the Exchange server will accept your e-mail.