Would K-9 add the support of ID extension in IMAP in the future? Someone else has already post the problem in the GitHub issues.
This extension is defined in RFC 2971
I know it sucks because the 163 mail(Netease) doesn’t follow the RFC standards, but considering that 163 mail has a lot of users(mostly in China), I think it would be more convenient.
Servers MUST NOT deny access to or refuse service for a client based on information from the ID command. Clients MUST NOT refuse to operate or limit their operation with a server based on the ID response.