Not an expert in mails myself but I also got trouble in past too when I moved from OJS 3.2 to 3.3 with Microsoft Office 365… and if I recall well, the problem had two main reasons:
a) Microsoft MTA is a mess (different kind of services under same umbrella… different standards and settings…)
b) OJS 3.2 and greater the phpmailer library have changed in OJS 3.3.
My personal conclusion (based on 20 years of observation) is some companies don’t play gentle with standards (because they are the standard) and then things go wrong…
I couldn’t manage to make OJS talk oauth2 in the way M$ demaned so I used a similar approach as you with a middle smtp relay.
Initially it fails but when I added the proper SPF records, M$ let me mail again… but I still don’t know why in hell I can’t user oauth2.
Here you have the issue:
You can also take a look to those posts talking about same/similar issue:
And PKP documentation (not specific for microsoft):
- https://docs.pkp.sfu.ca/admin-guide/3.3/en/email
- https://docs.pkp.sfu.ca/admin-guide/en/advanced-email
So if you find a solution or you can narrow the problem, I’m really interested in your research… so we can give PKP the right indications to fix this problem (at least till M$ MTA decide to change something else).
Cheers,
m.