IIS SMTP Service 5.5.2 rejected: need fully qualified

5.5.2 rejected: need fully qualified hostname” tends to be destination server specific and relates to the server name that the mail is sent from which is different from the email from name. Most mail servers will reject mail from a name that they cannot lookup in DNS as an anti-spam measure.

Open “Internet Information Services (IIS) 6.0 Manager” on the server.

Expand and then right click on “[SMTP Virtual Server #1]” and select “Properties” 

Select the “Delivery” Tab and then “Advanced”

Enter DNS (which you send mail from) “ex: company.com” in the “fully-qualified domain name” field.