Both of those email addresses from the hotel websites work just fine for reaching the hotels, but I also noticed that every reply either hotel sent me also cc'ed [email protected] so I think that serves as some de facto catchall email for the staff at both hotels.

Also, this is the signature in the reply the concierge sent me, which included a banner image at the bottom that incorporated both the Caption and HC into its design.

Lucas Liu 刘伟涛
Assistant Manager - Concierge 礼宾部副理
M: +86 182 2198 9204
E:[email protected]

Caption by Hyatt Zhongshan Park Shanghai 上海中山公园凯悦嘉荟酒店
No. 1525 Dingxi Road, Changning District, Shanghai
上海市长宁区定西路1525号

Hyatt Centric Zhongshan Park Shanghai 上海中山公园凯悦尚萃酒店
No. 1555 Dingxi Road, Changning District, Shanghai
上海市长宁区定西路1555号