Understanding how long it takes for the SMS Email alert to be sent

The email alerts sent to the last advisor who communicated with a student are polled every 15 minutes for unread messages. This interval is fixed. Users could have to wait up to 29 minutes for the message.

Why 29 minutes?
The system only polls for messages older than 15 minutes, and the polling interval is fixed at every 15 minutes of the hour. So if an email is sent at the 16th minute of the hour, it will not be picked up until it is polled at the 45th minute (because at the 30th minute, it is still only 14 minutes old).