Emails won't send from invoices or quotes

If I try to email from Invoice or quotes the caption comes up in Red : Error. Name Resolution Failure.
I hope it’s something simple but I really need some help with this ASAP please.

What software version number are you using?

Software version 15.0.90

You should update the software, it is currently 16.1.6 if I am not mistaken.

Thank you but how do I do that and will my accounts stay in tact

Yes, the update of the software is very easy. Just download from the Manage website and install over the location of the software. Your file remains untouched.

Fantastic that’s worked.
Thank yo so much.