The password requirements for Kerio Mail are not overly complex and align closely to many other systems and applications in use today.

The minimum password requirements are set out as follows

• must be at least 8 characters long
• must contain at least 3 of the following character types
  (lowercase, uppercase, numbers, symbols)
• cannot include any part of your name, surname or login name

I would suggest you read the following article on Passphrases as this will help give you a clear simple method to create quality password/phrase solutions rather than trying to unsuccessfully remember complex passwords.

https://help.wrenmaxwell.com.au/index.php?/Knowledgebase/Article/View/21/0/Password-or-Passphrase