Save Mail Message and Save Attachments activities are not intended to be used with which mail protocols?

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In the UiPath website https://docs.uipath.com/activities/docs/about-the-mail-activities-pack , it is mentioned that “Activities such as Save Mail Message and Save Attachments are not intended to be used with certain mail protocols”. They are not intended to be used with which protocols?

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This link describes the IP suite. But this doesn’t answer my question.