I am the person that will be helping you today.
As long as one person is receiving your emails, all should be. Often times, the culprit in such cases is that the email is blocked and/or filtered by the receiver's email server or application. I would suggest that you ask your customers to save your email address in their contact list to make sure that their filters do not block the email. In other words, when the email comes, it is probably redirected to their Spam or Trash folder.
If you need anything else in the future, please let me know.
Thank you for your time today.
Who are their email providers?
In other words, what comes after the @ sign in their email address?
I understand that this has not always been the problem. Just because their email systems were setup correctly at one time, doesn't mean they are still setup the same way. If you wish, I can take a look at one of your customer's computers remotely so that I can locate the culprit.
If you believe this was a waste, I can send up the refund request for you now.
What may have happened is that there is a problem with your distribution list. May I ask which application you use to send emails? (Outlook, Mac Mail, Internet browser, etc)
Thank you for the update.
May I start a remote screen sharing session with you so that I can better help you resolve this problem?
When the remote begins, a chat window will appear that we can use to communicate with each other.