rfc-1846

SMTP 521 Reply Code

A. Durand, F. Dupont

date1995-09 streamIETF areaapp wgmailext statusEXPERIMENTAL pages4 canonicalhttps://www.rfc-editor.org/rfc/rfc1846 doi10.17487/RFC1846

This memo defines a new SMTP ([1]) reply code, 521, which one may use to indicate that an Internet host does not accept incoming mail.