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I installed SMTP server on my Windows Server 2016. This server will be used by my web application to send emails to the users. For receiving emails I use different mail servers (MX records points to these different servers)
My question is about setting firewall. Will it be enough to open port 25 for only outbound? Do I have to open port 25 for inbound as well?
Thanks.
Gary
Posted 2019-02-04T16:34:29.823
Reputation: 21
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Welcome to Superuser!
This will work just fine for your purposes. You're correct, you have no need of port 25 inbound since you are not receiving mail.
All of the other verification stuff that mail servers will do to make sure you're not a dirty spammer involves checks against your server's reverse DNS, SPF/DKIM/DMARC, and the message contents - none of which involve connecting back to your mail server.
Mikey T.K.
Posted 2019-02-04T16:34:29.823
Reputation: 3 224