Using Imap4 to access Office365 Email

Before the company moved to Office365, we used to be able to connect to the Exchange Server using Imap4 as follows:

    Private Sub ReadOutlookEMail()
Dim imap4 As MailServer = New MailServer(ExchangeServerName, UserName, Password, True, ServerAuthType.AuthLogin, ServerProtocol.Imap4)
Dim oClient As MailClient = New MailClient("EG-AA1150422356-00388-F5A76D10CFC47CDB1B19F84C66DF4C8E")
Dim messageSubject As String = String.Empty
Dim messageBody As String = String.Empty

Dim infos() As MailInfo = oClient.GetMailInfos()

For iIndex As Integer = infos.Length - 50 To infos.Length - 1
Dim info As MailInfo = infos(iIndex)
Dim oMail As Mail = oClient.GetMail(info)

messageSubject = oMail.Subject
messageBody = oMail.TextBody

If (oMail.Attachments.Length > 0) Then
For Each att As EAGetMail.Attachment In oMail.Attachments
Dim sFileName As String
sFileName = messageBody.Substring(messageBody.IndexOf("From Date") + 10, 8)
sFileName = "C:\" & sFileName.Replace("/", "-") & ".CSV"
If Not File.Exists(sFileName) Then
att.SaveAs(sFileName, False)
End If
'End If
Next iIndex

Catch ex As Exception
SendMail("An error ocurred while reading E-Mail" & ex.Message)

End Try
End Sub

I tried connecting to Iffice365 as follows, but it just hangs:

        Dim imap4 As MailServer = New MailServer("", UserName, Password, True, ServerAuthType.AuthLogin, ServerProtocol.Imap4)

Any ideas?