Problems with outgoing emails - Please Help!!

About a week ago, a recipient of an email I sent forwarded my email back to me asking if it was intentional and I saw that my long email had been converted in a short series of meaningless (to me) symbols. The email I had actually written was nowhere to be found. After it happened a few more times, a technical person I know suggested checking my encoding to ensure it was set to UTF-8, which I did. I thought it worked but then I discovered that after hitting send, my emails were frequently becoming blank messages -- again, anything I had written was lost. Now both issues appear to be happening (seemingly at random... I haven't done a comprehensive review of when the issue arises, but it may be happening only on emails with attachments). Please help!