Why Are Users Receiving Undelivered Mail Return to Sender Notifications With PHP Memory Limit Error When Responding to a Ticket?

Overview

You might receive a report from users or customers stating that they are getting 'undelivered mail return to sender' notifications when replying to tickets from your Kayako Classic instance. The email notification would contain the following PHP memory error:

Command died with status 255: "/var/www/html/solanocoe.kayako.com/console/index.php". 
Command output: PHP Fatal error: 
Allowed memory size of 268435456 bytes exhausted (tried to allocate 134217736 bytes) 
in /var/www/html/solanocoe.kayako.com/__apps/tickets/library/Bayesian/class.SWIFT_Bayesian.php on line 704

This was a bug identified in version 4.93.07 due to a memory leak issue in the Bayesian tokenizer and in the SmartReply methods. It was fixed in version 4.93.16 (KAYAKOC-16629) and newer versions going forward. 

Information

If you are experiencing this issue and you are using Kayako Classic 4.93.07 or older versions, you need to upgrade your instance to the latest version.

• For Kayako Classic (Download), to upgrade your instance, please visit the Upgrading or Downgrading Your Kayako Classic Download article for guidance.

Note: To check the version of your Kayako Classic installation, please see the instructions provided in the KB article Identifying a Kayako Classic Version.