The original message was received at Mon, 20 Nov 2023 14:12:11 -0800 from m0342464.ppops.net [127.0.0.1] ----- The following addresses had permanent fatal errors ----- <mdell908@stanford.edu> (reason: 550 5.1.1 User Unknown) ----- Transcript of session follows ----- ... while talking to mxb-00000d03.gslb.pphosted.com.:

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DATA <<< 550 5.1.1 User Unknown 550 5.1.1 <mdell908@stanford.edu>... User unknown <<< 503 5.5.1 Need RCPT (recipient)