I carefully read the answers but I don't know how to apply them to my case. I have a link a link from Filemaker and I insert it in the body of the email, I have no control on this operation I cannot add anything that is not text.

If I generate the email on the client (Mac) and then send it the link is correct, the problem is by sending directly via SMTP. On other clients the link appears correct. Do you have any ideas? Thanks Corrado.