Your MTA should announce itself and DNS should agree. So your MTA says: HELO smtp.example.co.uk

smtp.example.co.uk will resolve to an A record (say a.b.c.d) and a reverse lookup will also work:

d.c.b.a.in-addr.arpa PTR smtp.example.co.uk.

Remember this is all about reputation, so if you also DNSSEC sign example.co.uk, then you will look like you care about your domain reputation.

Then do SPF, DKIM and DMARC. Note how the example for SPF stops at ~all and not -all. The rest is also superficial.

Anyway, I run email systems that do the job properly and it is not trivial and certainly not formulaic. There is no shortcut to getting an IP address/range trusted.

The advice on that page is ... good as far as it goes but woefully inadequate for running an email system. It's a good start.

Don’t waste your time.

I'd like to add the following, which I continually reference and has led to repeatable success:

https://www.linuxbabe.com/mail-server/setting-up-dkim-and-sp...

And as far as confirming it works, I continually rely on sending to a gmail address.

Under the three dots is "view original" which gives you

SPF, DKIM, and DMARC results.

(edit:formatting)

https://www.learndmarc.com/