Hello,
I am having the same problem, I have tested via telnet I can get out on 587, checked the Office 365 credentials, set it to "on device" instead of "on network".
I was also on 68.10.91 but now have upgraded to the SPAR of 68.11.23.
We are using STARTLS and SMTP AUTH.
When a user does a test scan we get 027-504.
Any help would be greatly appreciated.