Why does one of the recipients of notifications keep getting his email on the bounce list?

I just took it off but it seems that every couple of weeks, his email ends up on the bounce list & this is QUITE inconvenient.

There are many reasons why you might end up in our bouncelist.

But, the most common reason is often due to your email host flagging or rejecting our emails and marking them as spam so this forces the emails to stop and it is placed in our bounce list.

Please see the following guides below for more information:

https://www.jotform.com/help/262-How-to-Remove-Your-Email-Address-from-Bounce-List 

https://www.jotform.com/help/364-Why-I-am-not-Receiving-Email-Notifications 

https://www.jotform.com/help/208-How-to-Prevent-Email-Bouncing-Related-Issues

There are two other recipients using the same email host that get the emails.  Not sure the host thing is the answer!

I have checked your email notifications and I can see there is missing info, for example, the "Reply-to Email":

I would also suggest you to white-list our IP addresses, so you ensure that JotForm emails are not being blocked due to a security filter: Whitelisting-JotMails-IP-Addresses

The email may be blocked due to different reasons, for example, as shown above, the missing "Reply-to" email address may indicate that the form is spam, then the email gets blocked. 

However, if after doing this your email is still getting into our bounce list, please let us know, we will be glad to further check it. 

Why are the other emails that I have set up to get notifications receiving them and they do not have the reply-to entered?????  Can you tell me what this field means?

The Reply-to Email is usually the email address of the person who is submitting the form. If the reply field is filled, you can click on the Reply button in your email client to reply to that person.

If you notice your email address in the bounce list once again, you can contact us to check the 'reason' message. Do not remove it from the bounce list yourself, so we will be able to get the mentioned message for you.

If you would like to have more control over the email delivery, you might consider using your own SMTP sender on forms.

How to Setup SMTP for a Form

With that method the emails will be sent from your mail host server.