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Old 03-29-2011, 02:53 PM   #1
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Registered: May 2008
Distribution: Slackware
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A question about postfix and emails with large attachments...

Running Postfix 2.6.1 on Slackware 13.0. I noticed that if I send an email with a large attachment(namely more than 500 KB) from another computer using this postfix server as an smtp server, it takes up to an hour to send it. It's almost like postfix is configured to send large emails later with a lower priority. The client computer and postfix server are within a GIGABIT LAN so upload 500 KB isn't an issue.
Here's my /etc/postfix/
queue_directory = /var/spool/postfix
command_directory = /usr/sbin
daemon_directory = /usr/libexec/postfix
data_directory = /var/lib/postfix
mail_owner = postfix
myhostname =
mydomain =
myorigin = sub
inet_interfaces = all
mydestination = sub,,,, localhost
unknown_local_recipient_reject_code = 550
mynetworks_style = host
mynetworks =,
relay_domains = $mydestination,,
relayhost =
mail_spool_directory = /var/spool/mail
debugger_command =
sendmail_path = /usr/sbin/sendmail
newaliases_path = /usr/bin/newaliases
mailq_path = /usr/bin/mailq
setgid_group = postdrop
html_directory = /usr/doc/postfix-2.6.1/html
manpage_directory = /usr/man
sample_directory = /etc/postfix
readme_directory = /usr/doc/postfix-2.6.1/README_FILES
disable_vrfy_command = yes
smtpd_sasl_path = smtpd
smtpd_sasl_auth_enable = yes
smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
smtp_tls_security_level = encrypt
smtpd_tls_security_level = encrypt
smtpd_tls_auth_only = no
smtp_tls_note_starttls_offer = yes
smtpd_tls_key_file = /etc/postfix/ssl/server.key
smtpd_tls_cert_file = /etc/postfix/ssl/server.crt
smtpd_tls_CAfile = /etc/postfix/ssl/ca.crt
Any ideas of what would cause the delay?
Old 03-30-2011, 08:15 AM   #2
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Distribution: Ubuntu 10.10, Slackware 64-current
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I am not aware of a delay mechanism built into Postfix like this, but it sounds like you do have a bottleneck somewhere. Have you tried running a monitoring application like top while sending a message to see what your resource usage level is?


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