We have a series of similar workflows across multiple sites. The simplest of these is a single action: an email is sent when a list item is created. We have found on a few of these workflows (the simple one included) that the workflow repeatedly sends the email to the entire recipient group. This continues to happen until the workflow is manually terminated.
The same workflow exists on other sites (literally an export/import) and they work correctly.
For context, the recipients for the email are almost always the default members/owner/visitors groups that belong to that site. The list item has a recipient field where this is specified.
Any help would be appreciated. We are currently working with Nintex Support and Microsoft to understand the issue, but want to rule out anything simple on our side.
Update: Finally got some more information from Microsoft. They say they have found an error related to throttling - i.e. we have too many recipients or are sending too many emails in a short period of time.
Has anyone got tips on how to deal with larger volumes of emails? What is a good baseline to send per minute, etc. so we can avoid throttling? Is it better to change from the SharePoint mail service to the Nintex service and what do you need to be aware of doing this?