UTL_SMTP returns SMTP error for concurrent jobs running over 5 minutes

Hi,

We are using UTL_SMTP to email reports in Oracle. We are intermittently receiving the below error message. It occurs when the concurrent program runs longer than 5 minutes. Do you know why this is happening? Are there default SMTP time-out settings that reside on the mail or database server that would cause this? If so how do we change these settings?

Thank you,
Judy

ORACLE error 29278 in FDPSTP

Cause: FDPSTP failed due to ORA-29278: SMTP transient error: 421 Service not available
ORA-06512: at "SYS.UTL_SMTP", line 17
ORA-06512: at "SYS.UTL_SMTP", line 96
ORA-06512: at "SYS.UTL_SMTP", line 317