[issue21783] smtpd.py does not allow multiple helo/ehlo commands

[Milan Oberkirch]

New submission from Milan Oberkirch:

Sending HELO or EHLO more then once causes smtpd.SMTPChannel to respond with b'503 Duplicate HELO/EHLO\r\n' (see Lib/test/test_smtpd.py:124 for an example).

My interpretation of RFC 821, section 4.1.1.5 is that multiple HELO commands are fine outside a mail transaction and a second HELO is eauivalent to a RSET during a mail transaction (undoing any changes made by previous greetings).

I would propose to reject greetings during mail transactiond (thats what RSET is for) and else accept them. The question is how we should handle backwards compatibility here.

I am willing to work on this right after #21725.

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components: email
messages: 220754
nosy: barry, jesstess, pitrou, r.david.murray, zvyn
priority: normal
severity: normal
status: open
title: smtpd.py does not allow multiple helo/ehlo commands
versions: Python 3.5

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue21783>
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