If a user is sent email at an address that hard bounces with a permanent delivery error, that error tells Omnilert to stop sending email to that email address.
Therefore, on receipt of a permanent email delivery error ("Hard Bounce"), Omnilert will change the "Active" and "Validated" status for the address to "No".
If a user's not getting their emails, the first place to check is their user record on the Users page. Click on their username to view their account info, including all registered devices.
Make sure they have an address in their account, of course. Then also check if that address is marked as being "Active" and "Validated". If either says "No", then that's why they aren't getting emails from Omnilert.
If you see an asterisk (*) next to "No" in a user's email address status, that indicates a permanent email bounce error came to Omnilert at some point in the past.
To view the error details, just hover your mouse over the *
A popup will show you details about the permanent delivery error.
You may need to check with your local email admins to see why that error was returned to Omnilert.
If the cause of the email error has already been rectified, simply edit the entry to reset the user's email address to "Active" and "Validated" and you should be OK going forward.
Note: If Omnilert later receives another permanent delivery error, it will again revert the validation status to "No *".
Why does Omnilert disable emails this way?
The reason is simple: Spammers tend to send email to bad email addresses over and over.
That's one of the tell-tale signs of a spammer and many spam block systems will increase such a sender's "Spam score".
Of course, Omnilert does not send spam and operates by the rules. Sending repeated emails to bad addresses could result in all of Omnilert getting spam blocked or added to "spammer" lists. Obviously, that would be a bad result!
When a permanent email delivery error is returned, that forces Omnilert to stop sending mail to that email address until you (the admin) intervene.
How can this problem be prevented?
In truth, prevention is up to your recipients' email systems.
The best way to prevent this situation is for the recipient's server to properly return temporary delivery errors when addresses are suspended or mailboxes are full.
Temporary errors won't cause Omnilert to disable the address like Permanent errors do.
If your local email server is returning permanent errors (Hard Bounce) erroneously in place of temporary delivery errors (Soft Bounce), that configuration problem must be corrected to prevent this issue from recurring.