If you have configured the subject email and are getting the email indicating that XA is currently down every 5 minutes, most likely XA is being backed up. The problem may be more serious than that, but the message is indicating MES is unable to communicate with the iSeries. The mini-sync is defaulted to run every 5 mins, so you can expect this message every 5 mins until the error is corrected.
The message is part of the Oagis configuration and the only way to stop it is to turn it off by setting the minimum severity level to OFF.
If you find XA is not down or being backed up, please send the MES log files to help.desk@paperlessllc.com along with your company name, phone number MES version and service pack level.