IIS SMTP Virtual Server issue RRS feed

  • Question

  • User221306376 posted

    Good afternoon,

    I need some help.

    I created a SMTP Virtual server for relay emails send by multiples machines in our infrastructure to Gmail SMTP.

    Our domain = global.corp.

    Email domain = company.fr ( fake , of course ).

    So all emails with a sender "@company.fr" can be relay to the Gmail SMTP by this SMTP internal server , and we receives emails in our mailbox.

    My issue appears when the sender is another domain , for example emails sent by our Cisco server "@cisco.global.corp " ( domaine names are not reals but it's just an example ).

    Gmail rejected emails by this domain , even if we changed the security for allow them on Admin Google portal.

    We can change the domain smtp name in the Cisco server but they will have a lot of issues.

    Maybe someone already have this issue and know how to resolve it easily.

    Best regards,

    Friday, August 7, 2020 8:34 AM

All replies

  • User-848649084 posted

    If the relay server is allowed to relay emails to other external domains add a new *.com remote domain. Repeat for *.org, *.net, etc. as necessary.

    Remote Domains


    The SMTP Server feature can be added to any Windows 2003 or better server. I usually use the DirSync server if there is one.

    - Unlike Exchange, TLS for IIS 6 SMTP servers is not opportunistic. If the virtual server or a remote domain is configured to use TLS email will not be sent if the remote domain does not support TLS. Office 365 offers TLS, so we can use it.

    - The configuration above allows the IIS 6 SMTP server to send emails to the Internet for the remote domains configured, so you should add the public NAT IP address for this server to your existing SPF record to prevent non-delivery. Usehttp://whatismyip.com from the SMTP server to determine the NAT IP address.

    - Monitor the %systemdrive%\Inetpub\mailroot\Queue folder to ensure that emails are being delivered.

    1) If emails are not being delivered to Office 365 users, test sending email via Telnet. The IP address may be blocked by an Exchange Online Protection (EOP) blocklist and you will see that response from EOP. If so, send a delist request from your Office 365 admin account to delist@messaging.microsoft.com letting them know the IP address that should be delisted. In my experience, it takes up to 36 hours for Microsoft to delist it.

    2) If emails are not being delivered to external domains, ensure that you have a remote domain type (*.com, *.eu, etc.) configured for those email addresses.

    - You can enable logging in the properties of the SMTP virtual server for further troubleshooting. Use the NCSA Common Log File Format. IIS does not automatically groom or delete logs like Exchange does, so turn logging off when you’re done troubleshooting.

    - The best practice is to create an A record in internal DNS for smtp.yourdomain.com using the SMTP relay server’s IP, and configure all application servers and appliances to use that FQDN for email forwarding. That makes it easier to update in the future.

    Monday, August 10, 2020 2:36 AM
  • User-848649084 posted


    Is your issue solved?

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    If your issue still exists then try to refer the solution given by the community members.

    If then also you have any further questions then let us know about it.

    We will try to provide further suggestions to solve the issue.

    Thanks for your understanding.



    Thursday, August 20, 2020 2:14 AM