We are using Rebex version 2017 R1 and we are experiencing a strange behavior. We are trying to connect to Office 365 mail server using IMAP. This is our organization's mail server. We are able to connect to almost all the mail addresses, but there are some addresses that we get AUTHENTICATION(NO) when we are trying to connect to them. All the mail addresses are addresses that are used by our organization and we can connect to them successfully using office 365 web application.
What could be the problem?
I've seen that when IMAP was disabled for an individual user, check here;
you can enable the IMAP setting for this user in Exchange Admin Center (EAC). To do this, go to EAC > Recipients > Mailboxes > double click User or click Edit > Mailbox Features > under Email Connectivity > click Enable to enable IMAP for the user.
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