Changing the password of a chatmail account

Here it is:

Not unless you are also the administrator of the server.

They can’t change the password. Nobody can change the password except the chatmail provider. So if a scammer gains access to your account, they can’t lock you out, but I guess they could perform a denial of service attack by deleting your messages or do a message replay attack.

If you don’t use Delta Chat for a few months, then your account can expire and a scammer could in theory steal your address, but I doubt they could do anything malicious with that (like steal your identity) unless they also have your encryption keys and your contacts.