Fixing performance issues / Emails take long to load
By default, MailSuite Pro performs loading email message texts in background, to make sure user gets the message opened and displayed instantly upon selecting it in message list. The feature is known as prefetching, and as it's performed in background, it shouldn't conflict with the actions performed by users themselves.
However, with slow Internet connection or when the system is under heavy load, this could cause negative performance effect. If that happens, you might want to disable prefetching. To do so, add the following item to array defined in data/settings/config.php file:
'webmail.use-prefetch' => false,
One more thing that might help is disabling message threading. In case if message threading is enabled, MailSuite Pro requests the entire list of threads for the mailbox which might really slow things down. You can disable threading in user account settings, or altogether for the entire domain in AdminPanel.