I have a problem i would like to adress. I dont use cron or plugin for automated invoicesending.
When i select multiple customers for manual invoice sending and hit the email button, it takes a long time before anyting happens, get a server error (http 500 server error) and cant acces the joomla back end for a wile. When I acces VM invoice again, I only send a couple of incoices.

How can I address this problem?