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Outbound emails being NAT'ed to a different IP than Inbound

We have an Exchange server and two paths out to the internet. We are considering a configuration where emails would come in through one circuit and leave through the second circuit, being NAT'ed to a different IP. We realize there are some concerns here regarding these emails being marked as SPAM when other email servers run various DNS checks. Is this configuration acceptable and are there ways to protect against these emails from being marked as SPAM?

Thank You
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meade470
Asked:
meade470
1 Solution
 
AmitIT ArchitectCommented:
Exchange uses IP or fqdn to relay emails. If you are using smart host configure smart host ip. I don't think using different circuit will cause spam issue.
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meade470Author Commented:
Thanks for the quick response. But, in this configuration scenario, outside email servers will send to one IP/FQDN and then receive from a different IP/FQDN. I've seen where email servers will perform various DNS checks against incoming email to determine SPAM. Do you see any issues here?
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Simon Butler (Sembee)ConsultantCommented:
As long as the FQDN on the Send Connector has a valid PTR and matching A record, you should be fine. As you are using two connections with two different IP addresses I would probably have a different host name for your MX records.

Although I would see nothing wrong in having an MX record on both connections. If your router can handle the inbound SMTP traffic correctly then have email come in on both.

Simon.
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