If you are on the internal address book and cannot see a colleague, speak to your administrator.
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If you are part of an external organisation that receives your access to MX through your customer, then you can only see the internal address book and share data with those people. If your colleague needs an MX account and does not have one, please speak to your contact at the MX customer or an MX administrator.

See below on how to view the full list of Administrators in an MX customer.
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