Score:0

Setup DNS records for SMTP send-only server

do flag

I have website on hosting with domain exmpl.com. I have DNS record for exmpl.com:

exmpl.com MX(10) mail.exmpl.com
mail.exmpl.com A XX.XX.XX.XX
exmpl.com TXT v=spf1 +a +mx +a:hosting.server ~all

All incoming mail recived by hosting server.
Now all mail work over hosting server. I want to create SMTP server to send-only mail. I use Postfix. And create DNS record for exmpl.com:
smtp.exmpl.com A XX.XX.XX.XX
smtp._domainkey.exmpl.com TXT DKIM key

I have PTR on smtp.exmpl.com. How to setup spf record to send mail.
Example: i want to send mail from [email protected] to [email protected], but use my smtp server smtp.exmpl.com.
Do i need to create subdomain on hosting, smtp.exmpl.com and setup spf record for it? if yes, how to use this record in spf record of exmpl.com?

PS: SMTP server on Ubuntu 18 (This only-send SMTP server)

Score:0
jp flag

You need to add a:smtp.exmpl.com to your SPF DNS record for exmpl.com. You don't need + before a, mx, they are assumed by default.

You need to make sure that your PTR record matches forward resolution. If your postfix server is running on the host with IP 192.168.0.1 then smtp.exmpl.com should have A record 192.168.0.1 and PTR record for 192.168.0.1 should return smtp.exmpl.com. Your server should send smtp.exmpl.com as HELO.

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