Hello SmarterTools Team,

We are observing an inconsistency with bounce notifications for invalid recipient email addresses and would like your guidance.

Expected behavior:
When an email is sent to an invalid email ID within a domain, a bounce (NDR) notification should be delivered back to the sender.

Observed behavior:

• When testing from smarter mail, sending emails to invalid email IDs correctly generates bounce notifications to the sender.

• However, when performing the same test from Gmail, no bounce notification is delivered back to the sender.

Test details:

• Recipient: Invalid/non-existent email ID on our domain

• Sending clients tested:

  • smarter mail→ Bounce received ✅

  • Gmail → No bounce received ❌

As per internal guidance, we verified that bounce handling works correctly at the server level via smarter mail, but Gmail-originated emails do not appear to receive or relay the bounce notification.

Could you please clarify:

1. Whether this behavior is expected when emails are sent from external providers like Gmail?

2. If Gmail suppresses or handles NDRs differently for invalid recipients?

3. Whether any SmarterMail configuration is required to ensure bounce notifications are generated or relayed back to external senders like Gmail?

Looking forward to your insights.