552 5.2.0 ESMTP server not available AUP#O-1450
Does anyone have any information about the above error code?
From https://answers.microsoft.com/en-us/msoffice/forum/msoffice_outlook-mso_other-mso_2016/i-get-error-mail-could-not-be-delivered-552-520/9074628f-5dc5-472b-be49-4ece60bdc219, " A 552 email error is typically encountered when there is a problem related to an attachment in your email. Either it has exceeded the size limits of the remote server, or the file-type isn't allowed by the remote server. Some mail servers also seem to use this error code incorrectly when blocking a message due to triggering a filter such as a URL in the message being found in a domain black list. "
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