traveling around Germany

It sounds like you may be staying in smaller B&Bs or hotels. There may not be anyone around after a certain time (6pm, 8pm, 10pm), so they need to know when to expect you. You could ask them for a 'latest arrival time' guideline and see if that works. Otherwise, you'll just have to nail your plans down earlier than you wanted :-(

In smaller places the one or two people who normally greet new arrivals won't be at the desk waiting for you at all hours. They normally have other duties, have their own breaks, and only work so many hours a day. Often the same people are at the desk, serving breakfast and other meals, perhaps running the bar, doing backroom duties and many others. They would like to know when you will arrive so that they can arrange their schedule to be sure that you will be properly welcomed when you do arrive. It is very common, especially in Germany, especially at smaller places.

"I can send an E-mail when I get ready to go." When's that? Before you leave the US? That morning? If you can send an email, pick up a telephone card at a post office and call them that morning, or whenever you know. I remember a trip where I was staying in the Black Forest for a week and then going on to a Privatzimmer in Boppard. A couple of days before I left the BF, I called to confirm, and the lady asked what time I would arrive. I said about 1500. I guess she thought that, being American, I couldn't understand 24 hour time and muttered something about 5 (5 PM). I didn't want to explain on the phone that I really meant 3 PM and figured 5 was close enough. When I arrived at 3, she wasn't home. I had to call her on a number she had posted on the door and she came bicycling home from her mother's, where she had been visiting. When you are staying in a Privatzimmer, or a similar, small family run place with just a few rooms, that don't sit around all day waiting for you. If that's a problem, spend the money for a 5* hotel with 24 hr desk service.

Hi, I would not rely on sending an E-Mail as the way for "the places" to know when you would be arriving, unless you know they can receive E-Mail. Of course, they want to know when, ie., the hour, you would be arriving, the more exact the time the better. What I do as a courtesy to the owner/proprietor is to call them up, usually in the morning, or even the night before, and tell them when the train gets in and figure on top of that how long by public transportation and walking it would take me to be at the doorstep of the Pension/small hotel. You don't want them to be waiting for you, especially in the early evening. If you say 19:00, stick to it. They will expect you to do just that. If the answering machine picks up your call, leave a message. I tell them even where the train is coming from.