Newsletters are sent out on a first come first serve basis, so if another client on the same server as you has submitted a newsletter before you, those emails have to go through first before yours begin to send.
To check the status of your newsletter, go to http://www.yourdomain.com/en/actions/search.asp where you REPLACE www.yourdomain.com with your ACTUAL website domain or address.
Once a newsletter gets submitted, it enters the mail queue and is in the status of Submitted.
Once your newsletters start getting sent, it moves to the status of In Progress. It will stay in the status of In Progress until all the newsletters have been sent.
Once all newsletters have been sent, the newsletter moves to the status of Closed.
You can check the different states of your Newsletter by selecting the Status Detail in the drop down and clicking submit.
If you are curious about how many newsletters you can send with your Tendenci site, visit this help file.