Below:
* Findings of fact
* Representative messages from syslog
* postconf -n
* Output of tshark -- and if someone wants to complain about the length
of this message, they should consider all the bandwidth wasted by people
who quote entire messages in their replies :-)
Findings of Fact
1. For the past year, we have had increasing occurrences of mail
recipients not receiving email with attachments
2. Messages outbound from our internal mail server appear to be queued
and delivered
3. Logging into our mail relay shows hundreds of messages in a deferred
status due to timeouts sending message body
4. Text-only messages appear to succeed but this has not been
exhaustively tested
5. Some messages with attachments succeed, others don't but this has not
been exhaustively tested
6. Some destinations work regardless of message size, or number or size
of attachments
7. The most recent issue is sending a PDFs to a gmail.com account.
7a. One message is 87KB including attachment
7b. The other message is 272KB including attachment
7c. Text only messages to this user are delivered
7d. Some messages with attachments succeed
8. Our relay was using an old version of postfix, so I created a new
outbound relay using postfix 2.6.2
9. After scouring Google results, set MTU 1000 on all interfaces on the
relay
10. I attempted to get a packet trace, but none of the gmail servers
are responding on port 25--possibly they've blocked my site because of
repeated retransmission attempts
Representative messages from syslog:
Aug 1 06:58:11 relay postfix/smtpd[7489]: 3D59B1FBF2F:
client=server.company.com[10.0.0.2]
Aug 1 06:58:11 relay postfix/cleanup[7492]: 3D59B1FBF2F:
message-id=4a743ba6.1000...@company.com
Aug 1 06:58:11 relay postfix/qmgr[7454]: 3D59B1FBF2F:
from=sen...@company.com, size=278922, nrcpt=1 (queue active)
Aug 1 07:06:35 relay postfix/qmgr[7454]: 3D59B1FBF2F:
to=recipi...@gmail.com, relay=none, delay=504, delays=0.55/504/0/0,
dsn=4.3.0, status=deferred (mail transport unavailable)
Aug 1 07:19:33 relay postfix/qmgr[7454]: 3D59B1FBF2F:
from=sen...@company.com, size=278922, nrcpt=1 (queue active)
Aug 1 07:25:35 relay postfix/smtp[7536]: 3D59B1FBF2F: conversation with
gmail-smtp-in.l.google.com[209.85.221.36] timed out while sending
message body
Aug 1 07:31:36 relay postfix/smtp[7536]: 3D59B1FBF2F:
to=recipi...@gmail.com,
relay=alt1.gmail-smtp-in.l.google.com[209.85.210.42]:25, delay=2005,
delays=1283/0/361/361, dsn=4.4.2, status=deferred (conversation with
alt1.gmail-smtp-in.l.google.com[209.85.210.42] timed out while sending
message body)
Aug 1 08:09:33 relay postfix/qmgr[7454]: 3D59B1FBF2F:
from=sen...@company.com, size=278922, nrcpt=1 (queue active)
Aug 1 08:15:34 relay postfix/smtp[7650]: 3D59B1FBF2F: conversation with
gmail-smtp-in.l.google.com[209.85.221.73] timed out while sending
message body
Aug 1 08:21:35 relay postfix/smtp[7650]: 3D59B1FBF2F:
to=recipi...@gmail.com,
relay=alt1.gmail-smtp-in.l.google.com[209.85.210.90]:25, delay=5004,
delays=4283/0.01/361/361, dsn=4.4.2, status=deferred (conversation with
alt1.gmail-smtp-in.l.google.com[209.85.210.90] timed out while sending
message body)
Aug 1 08:47:31 relay postfix/qmgr[7454]: 3D59B1FBF2F:
from=sen...@company.com, size=278922, nrcpt=1 (queue active)
Aug 1 08:53:32 relay postfix/smtp[7772]: 3D59B1FBF2F: conversation with
gmail-smtp-in.l.google.com[209.85.221.11] timed out while sending
message body
Aug 1 08:59:33 relay postfix/smtp[7772]: 3D59B1FBF2F:
to=recipi...@gmail.com,
relay=alt1.gmail-smtp-in.l.google.com[209.85.210.16]:25, delay=7283,
delays=6561/0.01/361/361, dsn=4.4.2, status=deferred (conversation with
alt1.gmail-smtp-in.l.google.com[209.85.210.16] timed out while sending
message body)
postconf -n (note that during 2.6.2 installation, the original
configuration files were left in place--hence artifacts from 2.2.10
[r...@temp2hire tmp]# postconf -n
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 = 2
html_directory = no
inet_interfaces = dns.nmi.net
mail_owner = postfix
mailq_path = /usr/bin/mailq.postfix
manpage_directory = /usr/share/man
mydestination = $myhostname, localhost.$mydomain, localhost
mynetworks = 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
myorigin = $mydomain
newaliases_path = /usr/bin/newaliases.postfix
queue_directory = /var/spool/postfix
readme_directory = /usr/share/doc/postfix-2.2.10/README_FILES
relay_domains = $mydestination
sample_directory = /usr/share/doc/postfix-2.2.10/samples
sendmail_path = /usr/sbin/sendmail.postfix
setgid_group = postdrop
smtp_connect_timeout = 180s
smtp_data_done_timeout = 600s
smtp_data_init_timeout = 240s
smtp_data_xfer_timeout = 360s
smtp_helo_timeout = 900s
smtp_mail_timeout = 900s
smtp_quit_timeout = 900s
smtp_rcpt_timeout = 900s
smtp_rset_timeout = 180s
unknown_local_recipient_reject_code = 550
