Management
Selecting the Management node causes the right panel to split into a tree hierarchy view of domains on the left and the settings for the selected domain (or account) on the right.
(See Administration Console.)
Within the Management node, you can administer all your domains and accounts, modifying any settings as required.
Right-clicking in the middle panel will open the Accounts menu where you can add a new domain or account, make the selected domain the primary one, import or export account, etc.
Domains are expandable to a list of account types, which are in turn expandable if any of that type of account are defined within the domain. Items are expandable/collapsible by clicking the (+) or (-) symbol next to them, or by double-clicking.
Selecting a domain or account will effect the right hand panel to display settings for this item. You can modify these settings here.
You can use SHIFT/CTRL + click to multi-select accounts and change a certain setting for all at once (this setting shows highlighted yellow when doing so).
You can also create a group account, define members and use Templates within the Options tab of a group account to do mass changes. For example, one can add all domains as members of a temporary group account and apply a template to set all accounts of all domains to the IMAP type instead of POP3.
Another way how to perform mass changes is to use tool.exe/tool.sh.
The easiest way how to move users from one domain to another one is to cut and paste them. Use with care - big numbers of cut/pasted users (say hundreds and more) can cause long waiting without seeing any progress.