Emails being sent by numerous senders are being rejected with the following message:
bolt12a.mxthunder.net rejected your message to the following email addresses:
The address you sent your message to wasn't found at the destination domain. It might be misspelled or it might not exist. Try to fix the problem by doing one or more of the following:
This is only happening on two addresses, others on the same domain are not having this problem.
I think but cannot be sure that the problem is if mail is being sent by outlook.com, hotmail.com or office 365
I have exhausted all avenues with hotmail sender support as they keep referring to issues SENDING mail, not RECEIVING mail.
When the issue first ocurred the were using office 2010, I updated to Office 365 but still the same