How to set up SMTP Virtual Server with IIS

Exception: Mailbox unavailable. The server response was: 5.7.1

Check the following settings in IIS

IIS -> Default SMTP Server -> Properties -> Access
1. Authentication -> Anonymous access -> Checked
2. Connection control -> Only the list below -> Add current web server ip
Relay restrictions > Relay > - Only the list below -> Add current web server ip

Also add localhost ip here 127.0.0.1 . If DNS lookup doesnt work you can add alias for 127.0.0.1 in your
C:\WINDOWS\system32\drivers\etc\hosts file.

Also it is necessary to have these lines in web.config


<system.net>
<mailsettings>
<smtp deliverymethod="network" from="user@domain.com">
<network host="localhost" port="25" defaultcredentials="true">
</network>
</smtp>
</mailsettings>
</system.net>