Lost email address

I don't know whom to approach to sort out the problem. As VPE I'm trying to send out a member role report from my personal email to members@eastgateexpounders.org, but the email isn't recognized. Here's the error I get:

members@eastgateexpounders.org (members@eastgateexpounders.org)
The email address wasn't found at the destination domain. It might be misspelled or it might not exist any longer. Try retyping the address and resending the message.
If that doesn't work, contact the recipient (by phone or instant messaging, for example) to check that the address is correct. If the problem continues, forward this message to your email admin.
For Email Administrators
For more tips to help fix this issue, see DSN 5.1.1 Errors in Exchange Online and Office 365.
p3plibsmtp03-04.prod.phx3.secureserver.net gave this error:
<members@eastgateexpounders.org> Recipient not found. < x.co/irbounce >

Can you provide your club number so that we can assist you better.

sure, how do I find it?

Forgive me but I have to leave for a meeting. I'll be back. Thanks for the help you're already extending!!

Tell your club website admin that there appears to be a problem with your custom domain settings, specifically with the email settings. (There are two MX records when there is only supposed to be one.)

Whoever set up your custom domain will likely need to fix it.

I'm sure that will be a huge help. Thank you!!!