This is a known phenomenon. It occurs when the recipient has saved your email address under a different name in their address book. For example, if you send your emails as "Max Mustermann," but the recipient has saved you as "Müller GmbH" in their address book, your sender name will appear as "Müller GmbH" in the recipient's email view, even though your email address remains the same. This happens because the name in the recipient's address book overrides the original sender name.