Alert: Internal SMTP giving up on message: Unrecoverable error

Question:

Why are we seeing an alert from WSA stating "Internal SMTP giving up on message: Unrecoverable error"?

Environment: Cisco Web Security Appliance (WSA), All AsyncOS versions

Symptoms:

Email alert message similar to following are seen:
Internal SMTP giving up on message to user@domain.com [error message] Unrecoverable error

WSA periodically sends system generated email messages to the configured recepients. Recipient email addresses can be configured from "GUI -> System Administration -> Alerts -> Alert Recipients".

If the WSA is unable to communicate with a corresponding email server or any configured SMTP realy, an alert will be sent to all other configured users specifying an SMTP error. The alert is typically sent when multiple attempts at sending emails have failed.

Example:

user@localdomain.com and user@externaldomain.com are both configured to receive email alerts. If the mail server for externaldomain.com is not reachable, user@localdomain.com will receive an SMTP alert regarding the failure.

Reasons for the failure may include:

1. The corresponding mail server is down
2. Internal SMTP relay server is NOT accepting messages from WSA
3. A firewall is blocking port 25 (SMTP) access out to the internet

The WSA may need to be configured to use a trusted SMTP relay. This can be done from "GUI -> Network -> Internal SMTP Relay".