The Add-ons Manager tab is shown below.

Open
–Main Menu > Tools > Add-ons and Themes.
–☰ MyOffice Mail Menu > Add-ons and Themes.
Sections
–Extensions: extensions to the application functionality. The following extensions are built into the application:
•MyOffice Overlay: extension of the MyOffice Mail system.
•Provider for CalDAV & CardDAV: extension for CalDAV and CardDAV protocols.
–Dictionaries: dictionaries connected to the app to check spelling.
–Languages: extensions to support application languages.
Elements
–Button
: open the tools menu
–Switch
: enable the extension.
–Button
: open the Account Synchronization window.
–Button
: open the extension action menu.