Nigel Metheringham edited this page Nov 30, 2012 · 3 revisions
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I just noticed log entries that start off <= <>. Am I correct in assuming that the <> indicates that the envelope did not contain any From > data?


Yes. This indicates a delivery failure report (aka a bounce message ), as specified in RFC 2821. The reason for using empty sender addresses is to identify bounce messages so that they themselves do not cause further bounces. Empty senders are also used for other kinds of report which should not themselves cause the generation of bounce messages. For example, Exim uses them when sending out warnings about delivery delays.