I emailed Laserfiche Support about this and they recommended checking if TLS 1.2 is configured on the Workflow server and enabling it, if not. Info on that can be found here: https://support.laserfiche.com/kb/1013919/configuration-information-for-tls-1-2

I haven't looked into it yet but could be something to check.

(Legacy clients and devices will need to be configured to submit using the new smtp-legacy.office365.com endpoint to connect.) perhaps this is what you are looking for?

https://www.computerworld.com/article/3635608/how-to-make-sense-of-microsofts-upcoming-mail-security-changes.html

We suddenly (and unexplainably) started having this problem a few years back. Our IT could not find a solution.  I am now forced to always use the Try Catch activity for every email notification setting in Workflow and even then there is still the occasional unsuccessful email.  But not very often now that all the try/catch activities are in place.  I believe that it started after an upgrade, but I'm not sure if it was an O365 upgrade or a Laserfiche upgrade.  There were a lot of things happening, IT wise, around that time.

Hi Jeff,

I am also working with 2 customers who have this same thing going on. Haven't been able to nail down much of anything. We set up task error handlers for both customers based on the "Failure sending mail" message, but I'm not sure how well it's working - Workflow reports a warning on those email activities, but I can't tell if it worked on the retry.