Form Emails not being received by certain users

We have a form that is not being received by some users. Part of the form has the user input their email address. The form is sent to that email address. Some of the users get the email, but others don't. Two people in particular don't get them anymore as of last Friday. They were receiving them before. We are all on the same exchange server.

Thank you for contacting us.

Have you removed some of your email addresses from our bounce list? Your email addresses are not currently listed in our bounce list, so that the email sending should be fine.

Please note that you can also use your own SMTP sender on forms to have more control over the sending process.

How to Setup SMTP for a Form

If you need any further assistance, please let us know.

Sorry, forgot to update, that is what I ended up having to do. Didn't know there was a bounce list. Thanks.