Our company has a SMTP server that sends mail out on behalf of our customers. So a customer would log into our system, go to a specific section, and can fill out a form to send an Email to whoever they want as whoever they want from their domain, or any other domain for that matter. So if it was bobjones@domain.com he would just put in that address, he could also put in fakeguy@domain.com. However assuming he is putting in his correct domain sometimes the recipient marks it as spam because it is coming from our system not say their Outlook.

In order to resolve the delivery issues would it be accurate to tell them that they should create/update a SPF record on their domain as follows?

v=spf1 ip4: -all

At the moment we don't have a DNS A record pointing at this IP but I could create one if that would be better. In that case would it be this instead?

v=spf1 include:spf.ourdomain.com -all

Just tell them to update their SPF with your IP.

mailchimp or big mail forwarder just ask that, so only tell them to add


The line you wrote would remove other ip from their SPF, so it’s not a good idea to give them the entire line

  • I ended up creating an a record for spf.domain.com that points to our IP addresses and updated our customer documentation to use that. – Thorin Mar 13 at 17:33

First of all: don‘t give them a complete record. If they use one of your suggestions, then the problem will shift from „only mails sent by your system“ to „all mails that are NOT sent by your system“ as you exclude all of their own spf records.

And still not every admin is aware of spf records and what they mean and some will just blindly add your suggestion causing more problems than it solves.

Best practice would be to ask them to add your second suggestion.

With that they add your own spf record to their record. The advantage is: if you give them a concrete ip or host name that may change in the future or you may add a second or third host depending on the number of outgoing mails. Then you have to ask them to update their record every time something changes.

Just one more thing to clarify: when asking them to add include:ourdomain.com then this is NOT pointing to any ip or host name but to your OWN spf- record belonging to that domain, and in that spf record you would add something like ˋmxˋ or ˋa:mail.ourdomain.comˋ or ˋip:ˋ or any combination of it.

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