Is there a limit to the number of people you can send an alert to in 7.3? I ha

I'd recommend narrowing it down. Some ideas.
a) Review app server log files for error messages at this time.
b) Review current parameter configuration for conf.notifications.MAX_RECIPIENTS. Perhaps it is intentionally disabled with a value of 0.
c) Using a smaller sample, see if any notifications are sent.
d) Using a smaller sample, see if any emails are sent. If notifications are sent, but not email, there is a problem in email configuration.

Basically, we would be trying to determine the common scenario or info from error logs.

I'd recommend narrowing it down. Some ideas.
a) Review app server log files for error messages at this time.
b) Review current parameter configuration for conf.notifications.MAX_RECIPIENTS. Perhaps it is intentionally disabled with a value of 0.
c) Using a smaller sample, see if any notifications are sent.
d) Using a smaller sample, see if any emails are sent. If notifications are sent, but not email, there is a problem in email configuration.

Basically, we would be trying to determine the common scenario or info from error logs.