Use the complete SMTP response to diagnose outgoing mail rejected through SpamExperts. Authentication failure, a locked identity, content classification and a recipient-side rejection require different fixes.
IN THIS ARTICLE
01 Identify the failing stage
- Capture the sender, recipient, time and full delivery failure without removing its response code.
- Search outgoing logs for the message and inspect the recorded state.
- If authentication failed, verify the sending application's configured relay identity and TLS settings.
- If the identity is locked or the message classified as abuse, investigate the sender and content before requesting release.
- If the recipient server temporarily rejected delivery, inspect the outgoing queue and its retry status.
02 Test one correction
Send a small plain message to a controlled recipient after correcting the specific issue. Then test the normal business message. This helps distinguish a route problem from a particular attachment or content problem.
03 Example: an application reports success while the filter holds the message
The outgoing authentication settings include a Quarantine Response choice. Read the response together with the SpamExperts message state:
| Configured response | What the application may see | What to verify |
|---|---|---|
| Accepted, SMTP 250 | Submission appears accepted | The message can still be held in outgoing quarantine |
| Rejected, SMTP 550 | A sending failure or bounce | The filter can still retain the blocked message in quarantine |
These are configurable SpamExperts quarantine behaviours, not a rule that every 250 or 550 response means quarantine. Inspect the matching outgoing record and classification before retrying or releasing anything. A submission acknowledgement alone does not prove delivery to the recipient.
Common questions
Should I keep resending a delayed message?
Check whether it is already queued for retry. Repeated manual sends can create duplicates when the destination recovers.
Why does only one recipient domain fail?
That destination may have a policy or availability issue. Compare successful and failing destinations and retain the exact remote response.
Can you guarantee that a released message reaches Inbox?
No. The receiving system controls its own acceptance and mailbox classification. Support can investigate the recorded route and help correct the identified cause.
For escalation, provide the original failure and message identifier, not only a screenshot saying send failed. State whether the sender is a person, website, billing system or bulk-mail application. That context helps determine which authentication, content and usage controls apply without making unnecessary changes to all outgoing mail.