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5.  Add Files, you can add files up to the max size displayed in the limitations section 10).

6.  Limitations — Message Size, Quota and File Extension Limitations.

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11.  A Private Message is a message where the Message is not included in the email sent to the recipients.

When sending a Private Message:

The recipients will get a generic email telling them to click on the link to view the message.

You will get a read receipt when the recipient has viewed the message as well as when any attachments has been downloaded.

You can send a Private Message without any attachments.

It's not possible to send a Private Message with the permission that Anyone can download — in order to send a Private Message, authentication is required.

12.  When you're ready, please hit Send. If uploads are taking a long time, you can check the checkbox to "send when uploads are done".