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reverse lookup

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  • I have an asp.net application that generates emails.  Currently, it sends the email from me (using my dave@mydomain.com). 

    I am concerned that when I migrate to exchange online, the email process will be affected.  When a target server (perhaps at a customer site) to whom I am sending an email receives the email, it does a reverse lookup to verify ip matches the domain.  Since the domain will be hosted by exchange online, this will fail (I think).

    How will this work once I migrate.  I can't afford to have my emails sent to spam due to reverse lookup failure.

  • Hello Dave,

    Generally speaking this is what you'll use your SPF record for, as you can add your server to the SPF record to show that it is an authorized sender for your domain name.  You will see an IP mismatch, but this should be expected by your recipient, due to the fact that this is an extremely common scenario for large companies.

  • Thanks.

    What is an SPF record. When I edit my domain, I can edit a NS, MX, or A record.  I don’t know what you are referring to.

    When sending email, can I still send using localhost relay on the asp.net app, or do I need to use the exchange server to send messages?  If the latter, how do I set that up?  What IP or Name?  Port?

  • Hello Dave,

    Your SPF record is a DNS record, specifically a TXT record, that looks like this:

    v=spf1 include:outlook.com ~all

    By adding your server to the SPF record using SPF syntax, you'll appear as an authorized sender for your domain when someone does an SPF check.  And as for sending email with your Office 365 account, you'll want to give it your server name, port, username, and password.  You can get the server name and port from OWA, just sign in and go to Options and you can choose the option to show you your settings for POP, IMAP, and SMTP access.  You'll want to use the SMTP access settings.

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