Unable to export a mailbox folder in Horde webmail hosted in Plesk: Allowed memory size of X bytes exhausted

Symptoms

• When exporting a mailbox folder from Horde to an MBOX file, the operation fails with the following error message:

  File not found
  An error occurred during a connection to webmail.example.com.
  - Check the file name for capitalization or other typing errors.
  - Check to see if the file was moved, renamed or deleted.

• The mailbox folder contains a large amount of emails.

• The following error message appears in /var/log/psa-horde/psa-horde.log:

  PHP Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 222298112 bytes) in /usr/share/psa-horde/services/download/index.php on line 58

Cause

The memory_limit value configured in /etc/psa-webmail/horde/horde/php.ini is insufficient for this operation.

Resolution

Increase the memory_limit value:

1. Connect to the Plesk server via SSH.

2. Create a backup file of /etc/psa-webmail/horde/horde/php.ini:

   # cp -a /etc/psa-webmail/horde/horde/php.ini{,.backup}

3. Open the file /etc/psa-webmail/horde/horde/php.ini in a text editor. In this example, we are using the vi editor:

   # vi /etc/psa-webmail/horde/horde/php.ini

4. Increase the memory_limit value, for example to 512M or higher:

   memory_limit = 512M

5. Save the changes and close the file.

6. Try to export the mailbox folder again in Horde. If the operation fails again, increase
memory_limit to a greater value.