Email Not Being Sent

When I go to send an email letting all my pre-registered people know the gallery is ready, it says there are 88 of them.  But when I click on the link to email, where it says 'people who have pre-registered or imported for passcodes', it says 403!  Also says it will not send to (14) people that have no photos in the gallery.  

I *think* the 14 people are the class qr codes that don't have a photo attached yet.  and the 403 for all the students . . .but i did not have an email address in the csv file for the.

The biggest issue is that when I tried sending out an email, none of them seem to go through!  Help please :)

403 is a server error, contact your host and have them reset. You have tripped a mod security feature.

no, this isnt a server issue.  It’s the number of people who the gallery is telling me have either preregistered or were on the csv

I’m not sure it’s any of these things.  I sent out an email to everyone who had pre-registered BEFORE uploading the images and had no problems.  Once I uploaded the images, now emails won’t get sent.  
well, actually - there is 1 exception - one email actually shows up in the email log.  And that one is one of my email accounts that I used to log in and test viewing the gallery once the images were uploaded.  That is also the only email that is listed under "registered people who have viewed"

Please email me the following to look into it

1) The link / URL to your Sytist admin (where you log into your Sytist admin).

2) The admin username and password (or create me an admin account by clicking Admins in the upper right corner of the admin pages).

3) The name of  the gallery.