Hi AdamCarlson
Thanks for your post and Welcome to the Community Forum.
As for your concern, If you receive a message with a Rejected Code means that the recipient's end has rejected incoming email. Once the recipient whitelists emails with the domain apps.myob.com it usually stops the rejected messages.
To check this. Email an invoice to yourself. This will let you confirm the email address that the email is being sent from. Once you know this, provide it to the recipient so they can ensure it's whitelisted against any antispam systems they have set up on their email as well as add it to their address book within their email.
If still not working, so we can check if the emails are blacklisted on our end, can you please send us the impacted email addresses by Private Message.
Let me know if you require any further assistance with this. I'm happy to assist you.
If my response has answered your inquiry please click "Accept as Solution" to assist other users find this information.
Cheers,
Cel