how is someone able to use my email

[The Dad Fisherman]

A disreputable person or program can send out an E-Mail as anybody. I could send you an e-mail using your address and it would only take me about 10 seconds (and thats because I'm a crappy typist).

An E-Mail address is used more as a valid Destination than a Valid Source. Thats how a lot of the E-Mail viruses work. They collect e-mail addresses from a persons Mailbox (Pretty easy to do, anything w/ the "@" sign flags it as an address) and then propagates itself through the internet using its new collection of addresses. A lot of these viruses contain their own "Mail Server" built in.

I always make it a point to tell people to make sure they make there subject lines as descriptive as possible. If I get an e-mail from someone I know and it just has "Hi" or "Funny" or any other 1 or 2 word descriptions in the subject line I just delete it.