An undelivered or bounce message (often titled “Mail delivery failed”, “Undelivered Mail Returned to Sender”, or “Delivery Status Notification”) means the recipient’s mail system rejected your email or could not deliver it.
To fix it quickly, focus on the status code and the diagnostic message inside the bounce.
1) Identify whether it is a permanent or temporary failure
- 5.x.x — permanent failure (will not deliver until something changes).
- 4.x.x — temporary failure (often retries succeed later).
2) Common bounce reasons and what they mean
5.1.1 / “User unknown”
- The recipient address does not exist.
- Fix: verify spelling, confirm the mailbox exists, or contact the recipient via another channel.
5.2.2 / “Mailbox full”
- The recipient mailbox is out of storage/quota.
- Fix: ask the recipient to free space or increase quota; resend later.
5.7.1 / “Rejected”, “Blocked”, “Spam policy”
- The recipient server rejected the email due to policy or spam filtering.
- Fix: check your SPF/DKIM/DMARC records, use authenticated SMTP, and avoid spam-like content.
4.4.x / “Timeout”, “Connection refused”, “Try again later”
- The recipient mail server was temporarily unavailable.
- Fix: wait and retry; this usually resolves automatically.
3) How to read a bounce (what to copy)
In the bounce message, look for lines like:
- Status:
5.7.1
- Diagnostic-Code: explains why the remote server refused it
- Final-Recipient: the exact address that failed
4) Checklist for sending from GARMTECH email
- Send through SMTP‑SSL (port 465) with authentication.
- Use your service server hostname as the mail server name (as shown in My.GARMTECH).
- Ensure DNS has valid SPF, DKIM, and DMARC records for your domain.
- If you send a lot of mail, increase gradually and keep bounce rates low.
5) If you receive bounces for inbound mail
If someone tells you they cannot email you, the bounce is on their side. Ask them to forward you the bounce text — it will show whether:
- your domain has wrong MX records (mail goes elsewhere),
- your mailbox does not exist,
- the sender is blocked by spam policy.
Tip: You can always check your mailbox directly in GARMTECH.Email to confirm it receives mail.
