Known issues in Deep Castle Gen 2

SERVER PERFORMANCE DECREASED WHEN INDEXING ON

When the full-text search is already running or turned on during the server upgrade/installation, your server could face a temporary decrease in its performance due to the indexation of documents. This can take several hours depending on the volume of your data.

IM DOESN'T WORK

When the Digest-MD5 is disabled in the remote console - System - Advanced - Digest-MD5 then IM doesn't work and shows offline status.

The second issue regarding IM is when the user has in the remote console - Domains & Accounts - Management - Domain - User - for username this format: user@domain.com. The workaround is to set up only "user" in the username column without a domain.

TEAMCHAT AND CONTACTS DOESN'T WORK

This is caused by case sensitive MySQL database. IW expect to work with case insensitive database. Below you will find an article on how to change MySQL case sensitive DB to MySQL case insensitive.
https://support.icewarp.com/hc/en-us/articles/360014065658-Change-case-sensitive-DB-to-case-insensitive

TEST CONNECTION ON WEBDOCUMENT DOESN'T WORK

Unfortunately, this is known as BUG but it doesn't have an effect on the WebDocuments function. 

ISSUE WITH OTHER ACCOUNTS IN WEBMAIL

If you have lost added IMAP account in the webmail during the upgrade and you cannot add a new then go to the file system - to the mailbox of the affected user - ~webmail and delete accounts.xml. In this file are specified other accounts. After this, you will be able to add an IMAP account again.