Sometime around May 9, 2022, Microsoft made an unannounced change in the infrastructure of Exchange Online that caused slow loading of the Easy365Manager mailbox tab.
The change affects all user accounts with no user photo in Easy365Manager version 1.4.1 or earlier (the issue may or may not be seen in all tenants).
To fix this issue, download and install Easy365Manager 1.4.2 or later by going to the download page, entering your contact information and tenant name, and clicking the “30-Day Trial” button.