Gmail recipients see 'via (Interchangeable ID).d.bnc.salesforce.com' as the sender

This issue is evident when the customer is using Gmail and is not a Salesforce issue.

This is a security feature set by Gmail which displays the full email address of the sender.

"Gmail detected that the email was sent via another mail service. This means that the sender may be using a third-party email service to generate this message. For example, the message may have been sent through a social networking site which offers an email service or sent through a mailing list that you’re subscribed to.

Gmail displays this information because many of the services that send emails on behalf of others don’t verify that the name that the sender gives matches that email address. We want to protect you against misleading messages from people pretending to be someone you know."

For more information please refer help from GMAIL Extra info next to sender’s name.

As mentioned in the Google article following a best practice of using DKIM signing Create a DKIM Key in Salesforce combined with an SPF Sender Policy Framework (Sender Policy Framework (SPF) and Salesforce SPF Records) entry for Salesforce MTA IPs in the senders DNS should resolve the problem.

Another alternative could be to disable following email deliverability settings in Salesforce to remove the *bnc.salesforce.com from the sender domain.

This is to be performed by a Salesforce system administrator:

1. Search Setup for Deliverability
2. Deselect the Activate bounce management checkbox
3. Deselect the Enable compliance with standard email security mechanisms checkbox
4. Click Save