This article describes the error and its resolution, which appears when the large email(s) gets stuck into the mailbox associated with the email queue(s).
The help desk script tries to fetch the large email(s); however, due to memory_limit size limitations, it is unable to fetch the emails leading to memory exhaustion.
To resolve the issue, increase the memory_limit set in the php.ini.
The .htaccess or custom php.ini can also be used for this purpose, e.g., you may edit the .htaccess as follows:
php_value memory_limit 256M
.htaccess directives apply only to the folder in which the .htaccess file resides, and all the folders inside. This means that you may edit the .htaccess file and only the particular site will get affected where the .htaccess file is residing. It will not affect the functioning of any other site on that server. So, it allows you to set up a finely-grained tree of server directives, each subfolder inheriting properties from its parent.
The usage of .htaccess/custom php.ini depends upon the Server Configuration.