You can just put "Dear Sir or Madam", and you can write "to whom it may concern".

你可以就写“亲爱的先生或者女士”，也可以写“尊敬的相关人士”。

youdao

Dear Sir Or Madam, how are you?

尊敬的先生，女士们，你们好？

youdao

Dear Sir or Madam: The original and one copy of our leasing agreement1 are enclosed.

简要翻译附上我们租赁合同的原件及一份复印件，请查收。

youdao

Dear Sir Or Madam.

尊敬的先生或女士。

youdao

Dear Sir Or Madam.

尊敬的先生或女士。

youdao