Is Alipay's dunning letter signed or not?

Of course, you don't have to accept it, because Alipay belongs to the online lending platform, and the online lending platform generally won't send you a letter. These letters were sent to you by the company personnel entrusted by Alipay after you were overdue. Basically, it has no legal effect, just to intimidate you and put pressure on you to repay as soon as possible. When you encounter such a letter, you can directly refuse or ignore him.