Incomplete email content sent

When I send an email using EM client, the email recieved at the other end quite often has a large end portion omited. There seems to be no pattern as to where in the content this break occurs, and when I look at the email in the sent folder, it looks complete as I intended it. It is as if there is some non-printing character at play which when unwittingly included in an email acts as a break.
Anybody got any ideas on a fix?

Hello Bill,
are you able to replicate this issue? Are the messages incomplete even on your mail server/through webmail?
Could you provide screenshots of this issue, please?