Life on the Computer Farm: More Security Issues

 i first opened my main email address in 1998.  i'm still using it, and in all that time, i've never changed the password, which is was two innocuous four letter words, no number, no symbol, innocent enough that a child could speak them to Grandma.
  It worked well enough as long as i only opened the account at home, where the computers were only seen by family and maintained by the Serious Pro (MyGuy), who says

 Then i started occasionally using the account in a public place.
  And after that i started finding my address being used by someone else.
  Well, i was stupid.  It was ripe for being used.  i'm being more public now, despite the anonymity i strive for here.
  After adding the digital signature to my account, things were calm for awhile.
  But in the last 24 hours, i started getting more junk, returned mail from friends' closed accounts, stuff i hadn't sent, that i would never send.  i know my current contacts have to be getting the same junk, and at one level there's nothing i can do about it.
  Although if you have any ideas, i sure want to hear them.