https://bugs.exim.org/show_bug.cgi?id=2604
Bug ID: 2604
Summary: exim does not send DATA to target host when verify
callout hold and delivery cutthrough
Product: Exim
Version: N/A
Hardware: x86
OS: Windows
Status: NEW
Severity: bug
Priority: medium
Component: Transports
Assignee: unallocated@???
Reporter: david-exim-bugs@???
CC: exim-dev@???
Created attachment 1318
-->
https://bugs.exim.org/attachment.cgi?id=1318&action=edit
sample pcap of both SMTP sessions
Mail server setup:
sender --smtp--> inbound relay(exim) --smtp--> mailstore host(exim)
Inbound relay has a callout to verify recipient with 'hold' option set to keep
SMTP session alive for the message. Delivery is then cutthrough.
The inbound relay often does not send the DATA command to the mailstore host
and also misses out parts of the message. This causes at best SMTP
synchronisation errors.
Attached is a pcap of a simple test using telnet, but this also happens in
reality with real mail from real senders.
In the pcap:
- sending host is sarlonintman001 (2a05:e200:0:1::1)
- inbound relay is smtpin001 (2a05:e200:1:74::2:1)
- mailstore host is mailstore001 (2a05:e200:1:74::3:1)
The dialogue from sending host to inbound relay:
<< 220 smtpin001.a.snlmail.net ESMTP
>> ehlo asd
<< 250-smtpin001.a.snlmail.net Hello sarlonintman001.sargasso.net.uk
[2a05:e200:0:1::1]
<< 250-SIZE 52428800
<< 250-8BITMIME
<< 250-PIPELINING
<< 250-CHUNKING
<< 250-STARTTLS
<< 250 HELP
>> mail from:<asdadas@???>
<< 250 OK
>> rcpt to:<david@???>
<< 250 Accepted
>> data
<< 354 Enter message, ending with "." on a line by itself
>> Subject: test
>>
>> testing
>> .
<< 554 SMTP synchronization error
>> quit
<< 221 smtpin001.a.snlmail.net closing connection
The dialogue from inbound relay to mailstore host:
<< 220 mailstore001.a.snlmail.net ESMTP
>> EHLO smtpin001.a.snlmail.net
<< 250-mailstore001.a.snlmail.net Hello smtpin001.a.snlmail.net
[2a05:e200:1:74::2:1]
<< 250-SIZE 52428800
<< 250-8BITMIME
<< 250-PIPELINING
<< 250-CHUNKING
<< 250 HELP
>> MAIL FROM:<asdadas@???>
>> RCPT TO:<david@???>
<< 250 OK
<< 250 Accepted
>> testing
>> .
<< 554 SMTP synchronization error
>> QUIT
Note that the DATA command and the initial part of the message (subject line)
is missing.
Exim version 4.92 (Debian exim4-daemon-heavy package)
Configuration on relay host (one standalone file; Debian config is not used):
log_selector = +lost_incoming_connection +retry_defer
+sender_on_delivery +skip_delivery +smtp_confirmation +smtp_connection
+smtp_protocol_error +smtp_syntax_error +tls_peerdn
never_users = root
host_lookup = *
print_topbitchars = false
rfc1413_hosts = *
rfc1413_query_timeout = 5s
ignore_bounce_errors_after = 2d
timeout_frozen_after = 7d
smtp_banner = $smtp_active_hostname ESMTP
smtp_receive_timeout = 1m
tls_certificate = xxx
tls_privatekey = xxx
domainlist relay_domains = sargasso.pw
acl_smtp_rcpt = acl_check_rcpt
acl_smtp_predata = acl_smtp_ratelimit
begin acl
acl_check_rcpt:
# Accept local
accept hosts = :
# Accept hostlist
accept hosts = @ : 127.0.0.1
# Require it is a domain we relay for
require message = Relaying not permitted.
domains = +relay_domains
# Require that the user being sent to exists
require verify =
recipient/callout=10s,defer_ok,use_sender,hold,no_cache
message = Recipient <$local_part@$domain> unknown
# Accept message and cut-through
accept control = cutthrough_delivery
acl_smtp_ratelimit:
# Log all sender host ratelimits
warn ratelimit = 0 / 1h / readonly
log_message = RATELIMIT INFO: Sender $sender_host_address rate
$sender_rate / $sender_rate_period
# System-wide rate limit
defer ratelimit = 10 / 1s / $primary_hostname
log_message = RATELIMIT DEFER: System message rate $sender_rate /
$sender_rate_period.
message = System load exceeded. Try again later.
# Per sender host rate limit
defer ratelimit = 100 / 1h / strict / $sender_host_address
log_message = RATELIMIT DEFER: Sender host $sender_host_address
message rate $sender_rate / $sender_rate_period.
message = You have exceeded your maximum message rate. Please
try again later.
# Accept messages not rate limited
accept
######################################################################
# ROUTERS CONFIGURATION #
# Specifies how addresses are handled #
######################################################################
begin routers
system_aliases:
driver = redirect
domains = @
allow_defer
allow_fail
data = ${lookup{$local_part}lsearch{/etc/aliases}}
debug_print = R: system_aliases for $local_part@$domain
relay_virtual_domains:
driver = manualroute
domains = +relaydomains
route_data = mailstore001
same_domain_copy_routing = true
debug_print = R: relay_virtual_domains for $domain
transport = remote_smtp
no_more
smarthost:
driver = manualroute
domains = !@ : !+relay_domains
route_list = * smtpout byname
host_find_failed = ignore
same_domain_copy_routing = true
debug_print = R: smarthost for $local_part@$domain
transport = remote_smtp
no_more
begin transports
remote_smtp:
driver = smtp
message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
begin retry
* * F,4h,5m; G,16h,1h,1.5; F,2d,6h;
begin authenticators
begin rewrite
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