Write failed in network_biopair_interop with errno=104

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Write failed in network_biopair_interop with er...
\ nick (15 Jun 2007)
. \ Victor Duchovni (15 Jun 2007)
. . \ nick (18 Jun 2007)
. . . \ Victor Duchovni (18 Jun 2007)

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Subject:	Write failed in network_biopair_interop with errno=104
Group:	Postfix-users
From:	nick
Date:	15 Jun 2007

Hi folks,

postfix-2.1.5-4.2.RHEL4

I got this error in my maillog:

maillog.1:Jun 14 10:58:17 hpukhxdmz79 postfix/smtp[10019]: warning: Write failed in network_biopair_interop with errno=104: num_write=-1,
provided=4133
maillog.3:Jun 12 09:19:21 hpukhxdmz79 postfix/smtp[3024]: warning: Read failed in network_biopair_interop with errno=104: num_read=-1, want_read=7

Here is further detail of the transactions:

Jun 14 10:58:17 hpukhxdmz79 postfix/smtp[10019]: warning: Write failed in network_biopair_interop with errno=104: num_write=-1, provided=4133
Jun 14 10:58:17 hpukhxdmz79 postfix/smtp[10019]: 611F518060: lost connection with smtp.hp.com[161.114.21.254] while sending message body
Jun 14 10:58:17 hpukhxdmz79 postfix/smtp[10019]: 611F518060: to=<Synstar>, relay=cluster1a.eu.messagelabs.com[85.158.141.190], delay=14,
status=deferred (host cluster1a.eu.messagelabs.com[85.158.141.190] said: 421 Service Temporarily Unavailable (in reply to RCPT TO command))

Jun 12 09:19:21 hpukhxdmz79 postfix/smtp[3024]: setting up TLS connection to smtp.hp.com
Jun 12 09:19:21 hpukhxdmz79 postfix/smtp[3024]: warning: Read failed in network_biopair_interop with errno=104: num_read=-1, want_read=7
Jun 12 09:19:21 hpukhxdmz79 postfix/smtp[3024]: SSL_connect error to smtp.hp.com: -1
Jun 12 09:19:21 hpukhxdmz79 postfix/smtp[3024]: D7EE818060: Could not start TLS: client failure
Jun 12 09:19:22 hpukhxdmz79 postfix/smtp[3024]: D7EE818060: host mail555.messagelabs.com[216.82.248.45] said: 421 Service Temporarily Unavailable (in
reply to RCPT TO command)
Jun 12 09:19:22 hpukhxdmz79 postfix/smtp[3024]: D7EE818060: lost connection with mail555.messagelabs.com[216.82.248.45] while sending DATA command
Jun 12 09:19:23 hpukhxdmz79 postfix/smtp[3024]: D7EE818060: to=<lucia.alves>, relay=mail554.messagelabs.com[216.82.248.44], delay=4,
status=deferred (host mail554.messagelabs.com[216.82.248.44] said: 421 Service Temporarily Unavailable (in reply to RCPT TO command))

We use messagelabs as a smart host, except when sending to hp.com, then we connect direct to smtp.hp.com. The TLS connection to smtp.hp.com does not
work which is not an issue. Im unsure however whether the network_biopair_interop error is related to SSL or related to the same issue that is
causing 421 Service Temporarily Unavailable errors ? cluster1a.eu.messagelabs.com is our fallback_relay, but mail555.messagelabs.com is one of
messagelabs servers in our primary relayhost.

This is a bog standard Postfix install with TLS enabled.

I would appreciate any help on finding out what is causing this problem, and what I can do to fix it.

postconf -n below

Thanks,
Nick .

alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
command_directory = /usr/sbin
config_directory = /etc/postfix
daemon_directory = /usr/libexec/postfix
debug_peer_level = 5
fallback_relay = [cluster1a.eu.messagelabs.com]
html_directory = no
inet_interfaces = all
local_recipient_maps =
local_transport = error:local mail delivery is disabled
mail_owner = postfix
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
message_size_limit = 15240000
mydestination =
myhostname = mxtls.hpcds.com
mynetworks = hash:/etc/postfix/network_table
myorigin = hpcds.com
newaliases_path = /usr/bin/newaliases.postfix
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.1.5/README_FILES
relay_domains = hash:/etc/postfix/relay_domains
relay_recipient_maps = hash:/etc/postfix/relay_recipients
relayhost = [cluster1.eu.messagelabs.com]
sample_directory = /usr/share/doc/postfix-2.1.5/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
smtp_tls_CAfile = /etc/postfix/certs/postfix_public_key.pem
smtp_tls_cert_file = /etc/postfix/certs/postfix_public_key.pem
smtp_tls_key_file = /etc/postfix/certs/postfix_private_key.pem
smtp_use_tls = yes
smtpd_client_restrictions = check_client_access cidr:/etc/postfix/access_cidr reject
smtpd_tls_cert_file = /etc/postfix/certs/postfix_public_key.pem
smtpd_tls_key_file = /etc/postfix/certs/postfix_private_key.pem
smtpd_tls_loglevel = 1
smtpd_tls_received_header = yes
smtpd_tls_session_cache_database = sdbm:/etc/postfix/smtpd_scache
smtpd_use_tls = yes
transport_maps = hash:/etc/postfix/transport
unknown_local_recipient_reject_code = 550
virtual_alias_maps = hash:/etc/postfix/virtual