You have to change the maximum attachment size for your email accounts if you can’t send any attached documents via email. Plesk admins can change and set a memory limit to the attachment size for their Horde Webmail accounts.
To Set Limit to Attachment Size
1. Connect to your Linux server via SSH.
2. Edit the directory /etc/psa-webmail/horde/horde/php.ini and enter these settings:
upload_max_filesize = 256M post_max_size = 256M
3. Next is modifying the attach_size_limit value at the /etc/psa-webmail/horde/imp/conf.php file of Horde. In case you do not want to cap the limit(set it as unlimited), the limit should be “0“.
grep attach_size_limit /etc/psa-webmail/horde/imp/conf.php $conf['compose']['attach_size_limit'] = 0;
Note: If your requirement is specific, you can set exact values for the attachment size.
Moving on, these changes should reflect on all domains. It is why you have to modify the templates.
4. Create a new directory for the custom templates for webmail:
# mkdir -p /usr/local/psa/admin/conf/templates/custom/webmail
5. Enter/copy this template to the directory:
# cp /usr/local/psa/admin/conf/templates/default/webmail/horde.php /usr/local/psa/admin/conf/templates/custom/webmail/
6. Edit the FcgidMaxRequestLen directive in the custom template with the value specified in Bytes. (For example: 256MB= 268435456 Bytes)
# sed -i '/FcgidMaxRequestLen/c\FcgidMaxRequestLen 268435456' /usr/local/psa/admin/conf/templates/custom/webmail/horde.php
To finish things off, apply these changes within the template of all webmail accounts.
7. Run the command:
# plesk repair web -server
With this, you can easily set a memory limit to the attachment size for all Webmail accounts for Horde.