I clicked on that to see a form. I started to enter in my information, and the form requires that I enter my 9 digit zip code. Who really knows the last four digits? Screw that. I proceed with the form. Oh-uh.
I get this.

I repeat, it says, "Nothing which you have entered into the form will be saved." Pretty steep for not knowing those last four digits. Are we that concerned with someone outside the district contacting the representative? How about a redraw of the form with a red warning to enter in the digits?
There is of course no link or instruction to get back to the form. I use the browser back button (something I don't think anyone should really need to do...)

Ok, so the form includes a link to find your 9 digit zip code. I haven't seen this guy in a while. Nice to see he is till around. Of course, you need to go through 3 pages to get to your zip. And, now I am at the post office site with no easy way to get back (well, except for that back button).
So I click back three times and am now back at the form. I enter in my information and my note. Submit. Now this:
Hunh? Oh, I see this at the bottom of the form:


Not a horrible experience but not an easy one for sure.