Format for/creation of PTR and SPF records?

Question

Let's say that I have a server that resides at Linode that I use for my business, mybusiness.com. It has an IP Address of 1.2.3.4, and an A record of myserver.mybusiness.com. I own the domain name and host my DNS through DNSimple, and everything at this point works fine.

As a part of my business, I have a contract with othercompany.com. They control their own domain name, and someone else runs their DNS for them.

For this contract, I need to send emails as "them" (web@othercompany.com) from a process that is running on myserver. Myserver currently has Jenkins (for running the jobs) and Exim (for sending the emails) installed on it. We don't control the email addresses we're sending emails to; they're our clients' email addresses. Some of them are Google.

This was working fine for nearly a year. About a month or so ago, we started noticing bounces most specifically from GMail. Comcast has always presented a problem for us sending email as well.

SMTP error from remote mail server after end of data:
host aspmx.l.google.com [2607:f8b0:400c:c06::1a]:
550-5.7.1 [2600:3c03::f03c:91ff:fe73:138] Our system has detected that this
550-5.7.1 message does not meet IPv6 sending guidelines regarding PTR records
550-5.7.1 and authentication. Please review
550-5.7.1  https://support.google.com/mail/?p=ipv6_authentication_error for more
550 5.7.1 information. h1si10102273ywc.225 - gsmtp

So the first question I have is...Who should set up PTR and/or SPF records so that myserver.mycompany.com can properly send emails as web@othercompany.com and have places like GMail and Comcast accept those emails? Is it me (through my DNSimple account), or is it the company that controls their DNS? And secondly, what should those record(s) look like? Thanks!

Answer 1

In short:

1. reverse DNS (PTR) entries can be set by your server's ISP (Internet Service Provider).
2. SPF entries can be set in forward DNS service, use TXT type records for this.

The "other company", though, may have a policy to not allow sending e-mails claiming to come from their domain but from servers not under their control. This is smart and you shouldn't try to change that. Instead, cooperate with them - point your MTA to forward the messages to their server, they should allow you such a submission from given IP.