Hi Julia,
Your voters are probably being impacted by an ongoing issue with their email provider.
There is currently a problem with Microsoft’s email servers that is causing them to temporarily reject email from many senders, including OpaVote.
This has been going on since approximately January 12. Microsoft is aware of the issue and working on it but we have no way of knowing when it will be fixed.
Until then, users on Microsoft email platforms (Outlook, Live, and Hotmail) will not receive their email.
— Damien
Team OpaVote