Since there are too many different devices, languages, versions out there, We cannot make tutorial for each of time.
But the principle is the same:

1. find out Incoming and Outgoing server name, change both to h12.hksx.com.
2. change the password to new one.
3. try send/receive one email to yourself, it is done if successful.
4. if not successful, try change the POP3/IMAP/SMTP connection method to one of the followings:

Incoming mail server 內送郵件服務器

• server name 服務器名称: h12.hksx.com
• POP3 use port 110 (No-SSL) or 995 (SSL)
• IMAP use port 143 (No-SSL) or 993 (SSL)

Outgoing mail server 外寄郵件服務器

• server name 服務器名称: h12.hksx.com
• port 465 (SSL)
• port 587 (STARTTLS)
• port 25 (No SSL)