Configuring Postfix with external SMTP server

Manugal · 04-10-2010, 07:23 AM

Hi!

I'm trying to configure Postfix with a mail server that I programmed in C. The main.cf is set in this way :

Code:

relayhost = [myMailServer.localhost]
smtp_sasl_auth_enable = no
smtp_use_tls = no
disable_dns_lookups=yes
smtp_never_send_ehlo = yes

The problem arise when I launch mail command. This is what I wrote:

Code:

manugal@manugal-desktop:~$ mail -v -s "Subject" Manugal@myMailServer.localhost
Hello world!
.
EOT
Mail Delivery Status Report will be mailed to <manugal>.
manugal@manugal-desktop:~$

Mail doesn't arrive on my mailbox and if I check mail.log I found this:

Code:

Apr 10 12:11:58 manugal-desktop postfix/master[2756]: daemon started -- version 2.7.0, configuration /etc/postfix
Apr 10 12:12:05 manugal-desktop postfix/pickup[2758]: 5F94C21B28: uid=1000 from=<manugal>
Apr 10 12:12:05 manugal-desktop postfix/cleanup[2763]: 5F94C21B28: message-id=<20100410101205.5F94C21B28@manugal-desktop.localdomain>
Apr 10 12:12:05 manugal-desktop postfix/qmgr[2759]: 5F94C21B28: from=<manugal@manugal-desktop.localdomain>, size=488, nrcpt=1 (queue active)
Apr 10 12:12:05 manugal-desktop postfix/smtp[2765]: < myMailServer.localhost[192.168.1.11]:25: 220 myMailServer.localhost SMTP Service ready
Apr 10 12:12:05 manugal-desktop postfix/smtp[2765]: > myMailServer.localhost[192.168.1.11]:25: HELO manugal-desktop.localdomain
Apr 10 12:12:05 manugal-desktop postfix/smtp[2765]: < myMailServer.localhost[192.168.1.11]:25: 
Apr 10 12:12:58 manugal-desktop postfix/qmgr[2759]: warning: private/smtp socket: malformed response
...

I don't know why it doesn't receive response after HELO. In fact if I debug my mail server with gdb, I can see it sends a 250 response code. Moreover, I've tested my server both with traditional mail clients, as Thunderbird, and through telnet session and it works very well.

Who can help me?

blacky_5251 · 04-10-2010, 07:46 PM

Sounds like your SMTP server isn't working properly - I'm assuming Postfix is working OK.

Try using telnet to debug your remote server to see what the problem is. Try

Code:

telnet myMailServer.localhost 25

Then attempt to send an email by entering appropriate data. Use Google to search for EHLO communications, but if you've built your own server, it sounds like you know what the servers send to each other. Using telnet might show you more clearly where it is failing.

blacky_5251 · 04-10-2010, 07:50 PM

Sorry, you've tried telnet already.

Can you post the output of "postconf -n", and is your Postfix server able to send email directly (i.e. is it working?).

Should "smtp_never_send_ehlo = yes" be the other way around? Either "smtp_never_send_ehlo = no" or "smtp_always_send_ehlo = yes". My Postfix server uses my ISP to relay outbound email, and I don't use either of these setting (i.e. I use the defaults values which are the opposite to your settings).

Manugal · 04-11-2010, 05:10 AM

Hi! I've discovered a strange thing. To do an attempt I've tried to send, as a response, this string "\r\n250 OK\r\n" (so a 250 response code preceded by a CRLF). And now response seems arrive at the other side. Look at mail.log:

Code:

Apr 10 22:05:24 manugal-desktop postfix/smtp[2849]: 84A4821BDA: to=<Manugal@myMailServer.localhost>, relay=none, delay=0.02, delays=0.02/0/0/0, dsn=4.4.1, status=deferred (connect to myMailServer.localhost[192.168.1.11]:25: Connection refused)
Apr 10 22:05:36 manugal-desktop postfix/pickup[2846]: 70F9E21BDD: uid=1000 from=<manugal>
Apr 10 22:05:36 manugal-desktop postfix/cleanup[2859]: 70F9E21BDD: message-id=<20100410200536.70F9E21BDD@manugal-desktop.localdomain>
Apr 10 22:05:36 manugal-desktop postfix/qmgr[2847]: 70F9E21BDD: from=<manugal@manugal-desktop.localdomain>, size=488, nrcpt=1 (queue active)
Apr 10 22:05:40 manugal-desktop postfix/smtp[2850]: < myMailServer.localhost[192.168.1.11]:25: 220 myMailServer.localhost SMTP Service ready
Apr 10 22:05:40 manugal-desktop postfix/smtp[2850]: > myMailServer.localhost[192.168.1.11]:25: HELO manugal-desktop.localdomain
Apr 10 22:05:46 manugal-desktop postfix/smtp[2850]: < myMailServer.localhost[192.168.1.11]:25: 
Apr 10 22:05:46 manugal-desktop postfix/smtp[2850]: < myMailServer.localhost[192.168.1.11]:25: 250 OK
Apr 10 22:05:46 manugal-desktop postfix/smtp[2850]: server features: 0x1000 size 0
Apr 10 22:05:46 manugal-desktop postfix/smtp[2850]: > myMailServer.localhost[192.168.1.11]:25: MAIL FROM:<manugal@manugal-desktop.localdomain>
...

I don't know why replies must be sent in this way. Something is wrong.

However, in reply to you, I've used smtp_never_send_ehlo only for test, because I thought it was the reason of my problem. Moreover, my mail server is RFC821-compliant, so if I send a 502 response code to Postfix, it sends me HELO in place of EHLO, right?

blacky_5251 · 04-11-2010, 06:17 AM

I'm curious as to why your log shows "relay=none" on the first line of the log, when it should say "relay=myMailServer.localhost[ip.address.x.x]:25". Is it valid syntax to put the name of the relay server inside square brackets? My main.cf just has "relayhost = hostname.domain.com".

Manugal · 04-11-2010, 06:35 AM

Yes it's valid. From Postfix documentation:

"The form enclosed with [] eliminates DNS MX lookups"

I don't use DNS, but I've modified /etc/hosts to communicate with myMailServer.localhost.

I don't know why it says relay=none but the communication works anyway.

However, deleting square brackets doesn't resolve the problem.

Manugal · 04-11-2010, 06:40 AM

Perhaps that line, where there's relay=none, is a line from a previous try that I made. In fact smtp process ID in that line is different, as you can see. Ignore that.