Automatic SMTP Sending Hold Due to Anomalous Behavior
To protect email infrastructure and preserve the reputation of Utixo IP addresses, our SMTP servers perform automatic checks to detect suspicious sending activity, such as excessive failed messages or potential spam.
Conditions That Trigger the Block
The system will place a temporary sending hold if a high percentage of outgoing emails fail or remain in "deferred" status within one hour.
If the sending hold is triggered, the user will receive an error message like the following:
Sender email@domain.xx has an outgoing mail hold.
What Happens When the Hold Is Active
Outgoing emails are not deleted but are placed in a queue and held until the restriction is lifted.
Recommended Actions
- Identify the root cause (e.g., infected device, compromised script, unverified mailing list)
- Resolve the issue and verify that email sending is back to normal
- Wait for the system to automatically remove the block (typically within a few hours)
- Alternatively, you can open a support ticket to request manual unblocking
Warning: Unblock Request Policy
If a manual unblock is requested and spam behavior continues, the system will apply a new hold which cannot be manually removed for 24 hours.
Always make sure the cause has been eliminated before requesting an unblock.
Technical Information
Blocked users are listed in the server file system at the following path:
/etc/outgoing_mail_hold_users
