SMTP looping after two in a row ESMTP failures

[Carlos G Mendioroz-NOC <tron@fausto.me.gov.ar>]

We have spotted a problem with smtp ta from 2.99.55 pl1:
When in a session to a host using ESMTP, there are two
deliveries that fail in a row (i.e. one after the other)
the smtp transport somehow gets confused, and enters a
loop trying to deliver the second message again, and again, 
and...

Reproduce by:
1) stop scheduler (to have human time to post 2 messages)
2) place a couple of messages to an ESMTP capable site that rejects online
(e.g. 2vias.com.ar) to, say, an unknown user.
3) restart scheduler when messages are already at the queue.

Example smtp log:

06851e0000010288#       jobspec: F/150987-6675  2vias.com.ar
06851e0000110288#       150987-6675: <20010410134347Z150987-6675+1@choique.me.go
v.ar>
06851e0000210288#       (Connecting to `mail.2vias.com.ar' [64.76.45.218|25] Tue
 Apr 10 16:44:48 2001)
06851e0000310288r       220 mail.2vias.com.ar ESMTP Service (5.1.036) ready
06851e0000410288w       EHLO choique.me.gov.ar
06851e0000510288r       250-mail.2vias.com.ar
06851e0000610288r       250-DSN
06851e0000710288r       250-8BITMIME
06851e0000810288r       250-PIPELINING
06851e0000910288r       250-HELP
06851e0001010288r       250 SIZE
06851e0001110288#       smtpopen: status = 0
06851e0001210288w       MAIL From:<tron@choique.me.gov.ar> BODY=8BITMIME SIZE=34
7
06851e0001310288w       RCPT To:<pepe@2vias.com.ar> ORCPT=rfc822;pepe@2vias.com.
ar
06851e0001410288w       DATA
06851e0001510288r       250 MAIL FROM:<tron@choique.me.gov.ar> OK
06851e0001610288r       550 RCPT TO:<pepe@2vias.com.ar> User unknown
06851e0001710288r       554 DATA Transaction failed, no recipients given
06851e0001810288#        smtp_sync() did yield code 69
06851e0001910288w       RSET
06851e0002010288r       250 RSET
06851e0002110288#       jobspec: C/151010-6677  2vias.com.ar
06851e0002210288#       151010-6677: <20010410134402Z151010-6677+2@choique.me.go
v.ar>
06851e0002310288w       MAIL From:<tron@choique.me.gov.ar> BODY=8BITMIME SIZE=34
7
06851e0002410288w       RCPT To:<pepe@2vias.com.ar> ORCPT=rfc822;pepe@2vias.com.
ar
06851e0002510288w       DATA
06851e0002610288r       250 MAIL FROM:<tron@choique.me.gov.ar> OK
06851e0002710288r       550 RCPT TO:<pepe@2vias.com.ar> User unknown
06851e0002810288r       554 DATA Transaction failed, no recipients given
06851e0002910288#        smtp_sync() did yield code 69
06851e0003010288w       RSET
---start of loop---
06851e0003110288r       250 RSET
06851e0003210288w       MAIL From:<tron@choique.me.gov.ar> BODY=8BITMIME SIZE=34
7
06851e0003310288w       RCPT To:<pepe@2vias.com.ar> ORCPT=rfc822;pepe@2vias.com.
ar
06851e0003410288w       DATA
06851e0003510288r       250 MAIL FROM:<tron@choique.me.gov.ar> OK
06851e0003610288r       550 RCPT TO:<pepe@2vias.com.ar> User unknown
06851e0003710288r       554 DATA Transaction failed, no recipients given
06851e0003810288#        smtp_sync() did yield code 69
06851e0003910288w       RSET
06851e0004010288r       250 RSET
---end of loop element---