You will need to uninstall MAPI/CDO (Exchange Server MAPI) and install an Outlook 32bit client (Outlook 2013 or higher) on the AgendaX server. Also, the AgendaX mailbox needs to be migrated to Office 365 first, before you start migrating user mailboxes.

Then,

• Log in on the AgendaX Server with the AgendaX user. This is VERY important because Outlook profiles are user specific.
• Run Regedit and make sure that there is no value called MapiHttpDisabled under
• HKEY_CURRENT_USER\Software\Microsoft\Exchange or that its value is set to 0.
• Outlook 2013:
  • Run Regedit, go to HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Cached Mode
    and add a value called AllowAutoDiscoverForNonOutlook and set its value to DWORD 1.
  • Make sure that KB3114941 for Office 2013 32bit (https://support.microsoft.com/en-us/kb/3114941)
    is installed.
  • Add the following parameter to AgentX.ini:
    [Config]
    ForceIExchangeManageStoreEx=1
• Outlook 2016:
  • Run Regedit, go to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Cached Mode and add a
    value called AllowAutoDiscoverForNonOutlook and set its value to DWORD 1.
  • Make sure that KB3115279 for Office 2016 32bit (https://www.microsoft.com/en-us/download/details.aspx?id=53200)
    is installed.
  • Add the following parameter to AgentX.ini:
    [Config]
    ForceIExchangeManageStoreEx=1
• Outlook 2019 / Office 365:
  • Run Regedit, go to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Cached Mode and add a
    value called AllowAutoDiscoverForNonOutlook and set its value to DWORD 1.
  • Add the following parameter to AgentX.ini:
    [Config]
    ForceIExchangeManageStoreEx=1
• Then, create the Outlook profile and make sure that Exchange Cache mode is disabled in the Outlook profile. Enter the Outlook profile name (either in AgendaX Setup if you are setting up a new instance of AgendaX or in AgendaXCfg.exe (under MSX Version / Outlook MAPI Client / Outlook Profile Name), if AgendaX is already installed. The Standard- Name for the first Outlook- Profile that is configured is ‘Outlook’.
• Start Outlook with that profile and make sure that the profile works. When you are prompted for a password, make sure to check the ‘Remember password’ checkbox.
• Finally, close Outlook and restart the AgendaX Update Service

The permissions on Office 365 have to be set a bit differently than in an On Site Exchange environment. On Office 365, you will have to set permissions on folder level:

Please give the AgendaX user Reviewer rights on the top of the mailbox and the Inbox, and Editor rights on the Calendar folders.

The following, language-independent Powershell script will do this for you. You will have to initiate a remote Powershell session first with O365, using the Get-Credential, New-PSSession and Import-PSSession commands. Replace “agendax” on the 3^rd line in the following script with the name of your O365 AgendaX account:

Connect-ExchangeOnline
foreach ($Mailbox in (Get-EXOMailbox -OrganizationalUnit abc -ResultSize Unlimited))
{
Add-MailboxFolderPermission -identity "$($Mailbox.Name)" -AccessRights Reviewer -User agendax
Add-MailboxFolderPermission -identity "$($Mailbox.Name):\Calendar" -AccessRights Editor -User agendax
}
Disconnect-ExchangeOnline

"-OrganizationalUnit abc" limits the users to a specific OU (here "abc"). This can be omitted if you would like
to grant the permissions on every account in your organization.

If, instead, you would like to limit the users to users that have a specific SMTP- address, you can use the
following script:

Connect-ExchangeOnline
foreach ($Mailbox in (Get-Mailbox -ResultSize Unlimited | where-Object {($_.PrimarySMTPAddress -like "*@agendax.net")}))
{
Add-MailboxFolderPermission -identity "$($Mailbox.Name)" -AccessRights Reviewer -User agendax
Add-MailboxFolderPermission -identity "$($Mailbox.Name):\Calendar" -AccessRights Editor -User agendax
}
Disconnect-ExchangeOnline

Or, if you would like to limit the users to members of a specific distribution list, you can use the following:

Connect-ExchangeOnline
foreach ($Mailbox in (Get-DistributionGroupMember -Identity "NameOfDistributionList" -ResultSize Unlimited))
{
Add-MailboxFolderPermission -identity "$($Mailbox.Name)" -AccessRights Reviewer -User agendax
Add-MailboxFolderPermission -identity "$($Mailbox.Name):\Calendar" -AccessRights Editor -User agendax
}
Disconnect-ExchangeOnline

Please see also the following document: AgendaX Installation Guide V6.1