First of all, you need to write to Spotify support and resolve the issue about why the mail was returned to you. It's not worth opening a thread just like that. Many people have never encountered this and are not specialists, so I would write to support and solve this problem if I were you, so as not to wait long. In general, lately, I have noticed that many people have problems with mail on Spotify but even in the postal service. My friend recently exceeded the limit of sending tobacco by mail, and he had to pay a large fine. Therefore, you should always be aware of any issues. And occasionally, I read articles on this site -
https://mailingfacts.com about mailing.
