You didn't make it clear what program you are using to compose and send your emails. Most programs have a way to identify some kind of "signature" file that gets added to the bottom of what you write, or gets attached to the email when you send it. That sounds like what you might be talking about.
If that's it, then you need to look at the settings for your email program, find where it gets the "signature" from (it might be text that got entered into and saved by the program, or it might be coming from a file on your system, it will depend on the email program) and either clean out the signature, or tell the program you don't want it to include the signature information.
The details of how to do this vary from one email program to the next, and even if I knew what program you're using, unless I was already familiar with it, I might not be able to tell you how to get rid of the signature.
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