Okay... I am totally lost here! I have e-mail (interal e-mail and external e-mail) at my job. I am a bit nervous that if the company looks into my past e-mails that I have had and deleted. I have deleted documents and folders and sent them to the "trash bin". I have also deleted them from the "trash bin". My co-worker did the same thing but they ended up finding them even after she deleted them from her "trash bin"! (HOPE THIS MAKES SENSE)

My question: How did they retrieve them and how do I permanently delete them?

P.S. I know... I have learned a hard lesson here and I will no longer give out my work e-mail address to my friends who like to send "inappropriate" e-mails!

Typically, a company has what you would call a backup server. Depending on the size of your company will determine the system they use to back up-but usually there are backup tapes in which you can review at any time from any day. So, for ex: if you deleted inappropriate e mail on a Thursday, they could review a backup tape from Wednesday and it would still show that you had it in there.
So yes, you have learned your lesson. Tell your friends not to send inappropriate e mails to your work address. I would recommend setting up a Yahoo e mail account and have them send it there.
Good luck!

E-mail, both internal and external, are processed through a mail server. Before they can be placed in your mailbox, they have to be stored in a holding "bin" while its determined what mailbox to send them into.

There are a number of ways the mail server owners might use to check mail coming into or going out. Nothing you can do to stop that.