You can check Admin >> Logs >> Email Log and see if the email was sent. If the email was sent successfully in the email log then it was actually sent from the ERP. The issue then would likely be on the receiving end in that case. The customer might want to make sure the email recipient has email@example.com in their approved senders list.
However, it may not be realistic for you to notify every one of your customers and suggest they put “firstname.lastname@example.org” in approved senders list… Not sure that’s realistic for most of our users…
We do have this config:
You’ll notice a warning there: “don’t change this … or emails will fail DMARC validation and go to spam” - except, it sounds like that is what’s happening already, even with the default “email@example.com” setting.
Additionally, some folks have a problem with the “from” email address being firstname.lastname@example.org (as your customers don’t necessarily know who “email@example.com” is), even though the From [First Name] and [Last Name] indicate the user’s first name and last name.
So, I might recommend the best course of action here of changing the “email_from_address” to your own specific company-wide email address. That may help to get past your customers’ spam filters. Can you give this a shot and see if it works?