The dreaded spam inbox!

Ok so here is a weird one for you guys. :thinking:

When I send emails to clients/prospect directly from my Microsoft Outlook on my PC they go straight to the inbox on the prospect/customer.

BUT…
When i send with my exact same email (my personal job email) through SuiteCRM it goes straight the dreaded customers/prospects spam inbox.

I have configured and created:
- SPF
- DKIM
- DMarc
and in the SPF I have included the address for the CRM which lives on the same server as the email too.

i have run the test with sending a test mail to https://www.mail-tester.com and I get 10/10 score too. That is very peculiar though that then emails then end in the spam inbox from the CRM system not not from outlook. It just doesn’t make any logical sense.

The SPF record looks like this (Real names and IP redacted):
v=spf1 mx a ip4:555.555.555.555 a:server.something.com a:mail.something.com.uk include:crm.something.com -all

Any ideas maybe that could lead me in the right direction?

Thanks in advance…
Kind regards
PowerQuest