Overcoming the Sender Policy Framework: how to beautifully solve the problem of sending user letters with your mail service?

Question

SPF

The source data is this.
There is a SaaS service that, among other basic things, delivers messages from a SaaS user to his clients. Mail is delivered by the service's mail server, say, mail.saas.ru .
Let's say a user has his own sender address [email protected] , and sends a message to his client at [email protected] And here is an ambush: for some time now, the receiving Yandex server has been strictly monitoring compliance with SPF and immediately rejects the message.
How do I get around this now? I create a special address like [email protected] on my mail service and send a letter, specifying this address in From. In Reply-To, of course, I specify [email protected]. At the very least it works, but it looks like a crutch. How to do it beautifully, specifying the real address [email protected] in From , and at the same time not violate the SPF? I can't tell the Yandex admin "add mail.saas.ru to your txt-record"!
PS The same problem with sending to addresses in custom domains. According to Feng Shui, they need to add a rule for saas.ru to the txt record. It's kind of hard...

Answer 1

SPF was invented for this purpose, so that only hosts added (including implicitly added) to the SPF record could send mail on behalf of a domain user. On top of SPF, there is probably also DMARC. Wherever an SPF and/or DMARC policy exists and is verified, your SPF violation messages will not be accepted by the mail server. And if they are accepted, they will be marked as spam. In this case, you will not even know that they have not been read.
Therefore, here the correct solution is exactly the same as you have already applied. But you can't call him handsome. And it would be nice not to send a letter on behalf of a SaaS user, but by pressing a button or a link in a letter, open a ticket assigned to a SaaS user on your website. Those. so that there is no sender email [email protected] at all, but instead the recipient has the opportunity to contact him via a ticket.
And note, in addition to From and Reply-To, there is also Return-Path. Perhaps you need to specify your address in Return-Path, and [email protected] in From and Reply-To. Commercial mailing services do this.