Sending mails larger group of users - it takes a long time.

In tests JEM 2.2.0 (and earlier versions), I found the following. I hope to explain it clearly:

I have on our web site about 150 users.
If I create a new event (I set mail group for the mail about a new event for everyone)
or
I have already created an event and add (or send invitations) to event attendees lot ..

SO
- The system always sends mails (it's okay, I want ).

EDIT: Post I put in the wrong group, it belongs to the group: JEM 2.2.x on Joomla 3
BUT
- it takes a very long time to send it off. On page I do not know that the data is stored and the sending mail. "Ordinary" user's trouble and tends window must close or restore before it's done. I have tested it related to the amount of participants - the more mail, it takes longer.

Perhaps it would be good to be in the time between clicking the Save button, sending emails and restoring page has triggered an information window that the user did not close the page before the data is stored and distributed.

Do you know about this problem and you solve it?

Edit: Post I put in the wrong group, it belongs to the group: JEM 2.2.x on Joomla 3