The sendmail program needs to schedule events that happen at future times—for example, processing the queue. Internally, such events are set by specifying an interval to wait before the event is to begin. In the unusual instance that any such interval is less than or equal to zero, sendmail will log a message such as the following:

554 5.3.0 setevent: intvl=seconds

Here, the leading 5.3.0 is reported because such an error can happen during an SMTP session. The seconds will print as zero or as a negative number.

Should you ever see this error, the problem will most likely be found in a bad time specification in your configuration file.