Microsoft Dynamics CRM - Email notifications issue

Question

Hello

I work for an organisation that are using MS Dynamics CRM 2011 which is out of support, however, I am hoping someone can shed some light on an issue we have been experiencing for the last few months.

The system currently has a workflow which is designed to send out a reminder email to recipients who are nearing the expiry of a certain certification. This functionality was working just fine up until the last few months where it seems to send a copy of the same email hundreds of times to recipients that have an external email address in one go. Anyone with a company email address only seems to receive one reminder email which is correct.

We have had a look at the workflow setup and cannot see anything within this that could be causing the problems, however, not sure if there is anything specific we could check?

Any ideas what could be causing this please?

Thanks