For any system communications (emails or banner messages) with deliverability set to Upon Approval, they will be sent to the User Messages queue.

You are able to send out messages from your User Messages queue en masse by following these steps:

1) Go to Site > Communications > User Messages

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2) Filter the User Messages Queue by desired column(s)
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3) Mark the Select/Deselect All Checkbox
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4) Select Distribute from the Act on Selected Menu
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5) Select green Distribute button
Distribute Messages Dialog Box
Note: If you have more than 50 messages selected, be sure to mark the box to "Also distribute # messages from other pages" Distribute Messages Module