Sending physical mail seems really odd to me by now. I haven't turned on autopayment for half of my student loans because they require me to fill out a form and mail them in. It's such a hassle; I have to find time during the day to go purchase a single envelope and a single stamp, fill out the form, and then go drop it off. So much effort.
I'm sadden to say that I'm in the same boat as you. Too lazy to go to the post office, I just login to the website and do a manual payment for my loans.
I think, I'm going to just do it now that I realize how pathetic it is.
Not to derail this too much, but I still pay most all of my bills by check and snail-mail envelope. Until some companies stop charging a "convenience fee" that is more than the cost of a stamp and 1 minute of my time per month, of which I'm probably severely underestimating its worth, I'll continue to do so.