I'm developing an inbound email service to parse the email and create records in a custom object. This service was working fine in my developer org, but when I deployed this to a full sandbox for testing, Salesforce bounces the email saying
A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:
email@example.com (Undelivered): 551 Failed due to: SenderAuthorization
Initially, the 'Accept Email From' was blank (for testing purposes), but it still didn't work. I added our domain names and then added the specific tester's email address, still didn't work. Interestingly, it did work when I sent the email from my email address.
I came across this post,
Now due to a recent change on Salesforce side, our application servers are currently rejecting emails where the envelope-from in the email header has an email in the above format if an email is sent to E2S email address.
but I guess this scenario applies only for "Email to Salesforce".
Here is the screenshot of my configuration.
How do I solve this?