Hi everyone. Forgive my lack of knowledge on the subject and GP in general, but here goes:
Our org is suddenly entirely unable to email RM Statements. Our finance staff first noticed the problem on October 7th while trying to send out our Sept statment of accounts to customers.

We typically do this through Microsoft Dynamics GP > Tools > Routines > Sales > Statements.
PRINTING the statements to file or to screen works fine.
I have followed all the suggestions in the email troubleshooting guide and in this post that pertain to 'insufficient memory' (ie querying the tables for replyto addresses / special characters) but I have my doubts that this would be the issue. This email configuration has been running smoothly for years and has not been touched. The statments worked in September.
We're in a hybrid exchange environment. The timing is suspicious with the disabling of basic auth accross our tenant, but I cannot identify exactly what is going on. We are currently on version 18.4.1384, and since upgrading to this version, Our INVOICE emailing works properly via modern auth. It's just a the statements that are an issue.
Due to the volume of statements we need to issue, printing and sending them individually is not an option. Any help or direction is greatly appreciated.