By the way, «professional» includes correct grammar, spelling, and punctuation, as well as clear and correct contact information for both you and the person you are writing to. (robinresumes.com)
While German law indeed requires providing correct contact information it does not require the recipient to answer queries. (law.stackexchange.com)
You may also be asked to respond to a confirmation email sent to your inbox to ensure you are providing correct contact information. (articlesfactory.com)