Cannot send to AOL

[nitelife-dj]

Hi I'm new here and I'm needing a Techie to possibly shed some light on my problem, as I've searched the internet and I'm getting no joy at all. Basically, I have Office 2016 setup on my home computer and my office computer. My personal Outlook.com email is set up on both and I can receive email perfectly. However, My boss has a AOL email account and for some reason, whenever I either start a new email, or reply to one of his, I get this message:

Delivery has failed to these recipients or groups:
'Neil Wilson ("Neil W*****n" <n******er@aol.com>)'
The format of the email address isn't correct. A correct address looks like this: someone@example.com. Please check the recipient's email address and try to resend the message.

No matter what I send it returns the same....but works to everyone else.

However, if I send the message via outlook.com via webmail, it sends perfectly fine.
Anyone got any suggestions or ideas? I'm pulling my hair out.

Just a note before anyone asks me to delete the outlook account and re-set it up, I've done this countless times without any success.

Thanks guys and I await your responses.