Horde Mailbox Export Fails With "PHP Fatal error: Allowed memory size of ### bytes exhausted"

Symptoms

Horde mailbox export fails with an error message similar to the following error: (Replace $USER with the username/account that owns the email)

tail -f /home/$USER/logs/.php.error.log
[...............]
[03-Mar-2022 16:41:53 America/Sao_Paulo] PHP Fatal error:  Allowed memory size of 536870912 bytes exhausted (tried to allocate 198851159 bytes) in Unknown on line 0

Description 

This issue usually has to do with php-fpm memory limit for that account and can be resolved by simply increasing the memory_limit value. 

Workaround

Open below file and increase the memory_limit to 1 GB: (Replace $USER with the username/account that owns the email)

root@server [~]# grep -Ei memory_limit /var/cpanel/php-fpm.d/$USER.conf
php_value[memory_limit] = "1G"

Restart the service: 

/scripts/restartsrv_cpanel_php_fpm

In case PHP-FPM is not running the following steps can be attempted alternatively: 

/usr/local/cpanel/3rdparty/etc/php.ini 

/usr/local/cpanel/bin/install_php_inis

Note: If the above changes alone does not resolve this issue then it might be also necessary to update the memory_limit in one or both of the following files:

/usr/local/cpanel/3rdparty/php/73/etc/horde/php.ini

/usr/local/cpanel/3rdparty/php/74/etc/horde/php.ini