It costs a little more, but you'll always know that your manuscript arrived safely at its destination. Better yet, an editor is much more likely to remember your story if he has to stand in line and sign for it, unlike all the other nameless, faceless submissions that quietly slip into his mailbox unannounced. Editors are always looking to discover the next Stephen King, and thus have an insatiable appetite for new authors. If you haven't sold anything yet, make sure the editor knows right up front in your cover letter that you are a beginner. This insures that your story will get all the attention that a new writer deserves.
Editors are busy people.
Often too busy to read long manuscripts. Help them out by telling them all about your story in your cover letter so they can decide how much they really want to read it. Editing is a lonely profession. A phone call from an enthusiastic author to check up on the status of a submission is just the thing to cheer them up. If you can't reach the editor right away, be persistent.