postmaster@servername.mydomain.com as "from" address

Question

Very first time in 6 years, my client has reported that they are receiving email from my asp.net web applicaation with "from" id as "postmaster@servername.mydomain.com". Though, the mail id I use to send emails are "support@mydomain.com".

Not all the emails are delivered with postmaster@ as "from" address.

The "to" address of these kind of emails are like donotreply@ . So if a "to" address belongs to "donotreply" category, will SMTP will change the original "from" address to "postmaster@"?

We haven't faced this anytime before but why is it occurring now? I googled and found https://webmasters.stackexchange.com/questions/2030/should-i-set-up-standard-email-accounts-what-are-they and Do I really need webmaster@domain.com, postmaster@domain.com, etc. emails? but not sure what it has to do with my SMTP.

Can someone help me understand why it is happening?

Answer 1

http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/6bb0d71f-d3d7-4f59-aa01-4d5c022274a4.mspx?mfr=true

From the above link,

To rename the default domain

1.In IIS Manager, expand the SMTP virtual server, and then click Domains.

2.In the details pane, right-click a domain name, and then click Rename.

3.Type a new name for the default domain.

For me the domain name was "servername.mydomain.com" and I modified it as "mydomain.com"