Difference between revisions of "Outgoing SMTP Authentication"

(Cleaning up formatting and removing uneccesary "commentary" and reformatted and reordered for readability)
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The outbound destination should be the canonical address.  postfix will resolve CNAMEs to canonical addresses and then use that to lookup the username and password .
 
The outbound destination should be the canonical address.  postfix will resolve CNAMEs to canonical addresses and then use that to lookup the username and password .
 +
 +
 +
Godaddy example:
 
<pre>
 
<pre>
Godaddy example:
 
 
 
smtpout.secureserver.net is really smtp.starfieldtech.com, so make sure you enter smtp.starfieldtech.com
 
smtpout.secureserver.net is really smtp.starfieldtech.com, so make sure you enter smtp.starfieldtech.com
  
Line 23: Line 24:
 
== Setting a relay host ==
 
== Setting a relay host ==
  
Set the relay host in the admin console, [[MTA]] tab to point to your ISPs outgoing mail server.  Your ISP can tell you the proper value for this.  You may have to set the port, as well.
+
Set the relay host in the admin console, [[MTA]] tab to point to your ISPs outgoing mail server.  Your ISP can tell you the proper value for this.   
 +
 
 +
You may have to set the port, as well. From the command line:
  
 
  zmprov ms server.domain.com zimbraMtaRelayHost external.relay.com:#
 
  zmprov ms server.domain.com zimbraMtaRelayHost external.relay.com:#
  
== Enable TLS ==
+
== Enabling SMTP authentication ==
This is needed for gmail
 
As Zimbra user:
 
  postconf -e smtp_use_tls=yes
 
 
 
== Enabling smtp authentication ==
 
  
 
''Run all these commands as the [[zimbra user]]''
 
''Run all these commands as the [[zimbra user]]''
  
 
Create a text file mapping which name/password should be used for each given outbound destination:
 
Create a text file mapping which name/password should be used for each given outbound destination:
  echo mailrelay.example.com ''username:password'' > /opt/zimbra/conf/relay_password
 
  
Create a postfix lookup table
+
echo mailrelay.example.com ''username:password'' > /opt/zimbra/conf/relay_password
  postmap hash:/opt/zimbra/conf/relay_password
+
 
 +
Create a postfix lookup table:
 +
 
 +
postmap hash:/opt/zimbra/conf/relay_password
 +
 
 +
Test that the lookup table is correct:
  
Test that the map is okay
+
postmap -q mailrelay.example.com /opt/zimbra/conf/relay_password
  postmap -q mailrelay.example.com /opt/zimbra/conf/relay_password
 
  
This should return ''username:password'' if done right
+
This should return ''username:password''.
  
Make postfix use the above
 
 
  postconf -e smtp_sasl_password_maps=hash:/opt/zimbra/conf/relay_password
 
  postconf -e smtp_sasl_password_maps=hash:/opt/zimbra/conf/relay_password
 
  postconf -e smtp_sasl_auth_enable=yes
 
  postconf -e smtp_sasl_auth_enable=yes
 +
postconf -e smtp_cname_overrides_servername=no
  
postconf -e smtp_cname_overrides_servername=no
+
''smtp_cname_overrides_servername=no'' is used because many smtp servers forward the connection different server than the one set in the smtp_sasl_password_maps file.  
This last one might be MORE THEN VERY IMPORTANT if you want it to work and
 
not to loose 3 days searching the internet and trying every possible configurations
 
you can find as I did!. We may say it's not the best secure way to do it but you can
 
improve security with smtp_tls_per_site once it works and once you know that the
 
authentication works. If you apply smtp_tls_per_site settings then
 
smtp_cname_overrides_servername may become obsolete.
 
  
The purpose of using smtp_cname_overrides_servername=no is because many smtp servers use load balancing or other technology witch cause your machine to send or forward the outgoing emails to a server having a different name then the one set in the smtp_sasl_password_maps file. Example of the problem :
+
Example of the problem :
  
 
/opt/zimbra/conf/relay_password :
 
/opt/zimbra/conf/relay_password :
smtp.gmail.com blabla@gmail.com:password
 
  
but postfix connect to gmail-smtp.l.google.com
+
smtp.gmail.com username@gmail.com:password
  
What happens is that postfix will not send the authentication info contained in smtp_sasl_password_maps file because it as no entry for the server gmail-smtp.l.google.com but has one for smtp.gmail.com
+
but postfix connects to gmail-smtp.l.google.com
  
Using directly gmail-smtp.l.google.com everywhere COULD resolve the problem too but may cause two others problems. First, the server gmail-smtp.l.google.com may not accept direct connections. Second, the day it goes down you are screwed! Using the server CNAME entry or whatever it can be as smtp.gmail.com in this exemple is a much better way to make it works.
+
Postfix will not send the authentication info contained in smtp_sasl_password_maps file because it as no entry for the server gmail-smtp.l.google.com but has one for smtp.gmail.com
  
Finally if youre using a Zimbra package (some readers may land here looking for POSTFIX config) and if you have been searching the internet or are about to do so for troubleshooting youre installation, DON'T use the brakets [] for the server name definition as we can see in many places. Exp.:[smtp.gmail.com]
+
If you apply smtp_tls_per_site settings then smtp_cname_overrides_servername may become obsolete.
  
By the way if you intent to use smtp.gmail.com make it works on the port 587. Port 25 gave me timeout as well did port 465. Exp.: relayhost=smtp.gmail.com:587
+
Restart postfix:
  
Good luck!
+
postfix reload
- Frederik Bacon -
 
  
 +
== Enable TLS ==
  
Restart postfix:
+
As Zimbra user:
  postfix reload
+
 
 +
postconf -e smtp_use_tls=yes
 +
postfix reload
  
 
== Troubleshooting ==
 
== Troubleshooting ==
  
 
After sending a test message, check the [[Log Files]] for the error:
 
After sending a test message, check the [[Log Files]] for the error:
  (Authentication failed: cannot SASL authenticate to server ...: no mechanism available)
+
(Authentication failed: cannot SASL authenticate to server ...: no mechanism available)
  
 
You can fix this problem by tweaking the auth mechanisms that postfix is willing to use.  First check what auth mechanism postfix is configured to use - by default, you will see:
 
You can fix this problem by tweaking the auth mechanisms that postfix is willing to use.  First check what auth mechanism postfix is configured to use - by default, you will see:
  
  $ postconf smtp_sasl_security_options
+
postconf smtp_sasl_security_options
  smtp_sasl_security_options = noplaintext, noanonymous
+
smtp_sasl_security_options = noplaintext, noanonymous
  
 
Since noplaintext is present, postfix will refuse to use a mechanism that sends passwords in the clear.  If your upstream relay host only supports PLAIN or LOGIN mechanisms (both of which send password in the clear), you have to remove noplaintext from smtp_sasl_security_options:
 
Since noplaintext is present, postfix will refuse to use a mechanism that sends passwords in the clear.  If your upstream relay host only supports PLAIN or LOGIN mechanisms (both of which send password in the clear), you have to remove noplaintext from smtp_sasl_security_options:
  
  $ postconf -e smtp_sasl_security_options=noanonymous
+
postconf -e smtp_sasl_security_options=noanonymous
  $ postfix reload
+
postfix reload
  
 
If you are concerned about password-in-the-clear and your upstream relay host offers TLS, you might be interested in this [http://www.postfix.org/postconf.5.html#smtp_use_tls smtp_use_tls] variable.
 
If you are concerned about password-in-the-clear and your upstream relay host offers TLS, you might be interested in this [http://www.postfix.org/postconf.5.html#smtp_use_tls smtp_use_tls] variable.
  
 
See also [http://www.postfix.org/SASL_README.html#debugging].
 
See also [http://www.postfix.org/SASL_README.html#debugging].
 +
 +
Don't use brackets [] around the server name definition as seen in many places. Exp.:[smtp.gmail.com]
 +
 +
  
 
== AT&T Yahoo DSL Specific ==
 
== AT&T Yahoo DSL Specific ==
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  (lost connection with smtp.att.yahoo.com while receiving the initial server greeting)
 
  (lost connection with smtp.att.yahoo.com while receiving the initial server greeting)
  
Some ISP's do not implement TLS properly on port 465 (AT&T Yahoo DSL in particular although it is the only port their documentation advertises as available), and normal mail clients do not notice this when making an SSL connection. Postfix, however is very touchy about the handshaking. Port 587 (standard secondary SSL SMTP port) works properly though.
+
Some ISP's SMTP servers do not implement TLS properly on port 465 (AT&T Yahoo DSL in particular); mail clients handle this when making an SSL connection, however Postfix loses the server connection in this case. Port 587, the standard secondary SSL SMTP port, does work properly with TLS.
  
The proper commands for AT&T dsl customers in the above setup are:
+
The proper commands for AT&T DSL customers in the above setup are:
  
Change
+
Change:
  
 
  zmprov ms server.domain.com zimbraMtaRelayHost external.relay.com:#
 
  zmprov ms server.domain.com zimbraMtaRelayHost external.relay.com:#
  
To
+
To:
  
 
  zmprov ms server.domain.com zimbraMtaRelayHost smtp.att.yahoo.com:587
 
  zmprov ms server.domain.com zimbraMtaRelayHost smtp.att.yahoo.com:587
  
And add
+
And add:
  
 
  postconf -e smtp_sasl_mechanism_filter=plain,login
 
  postconf -e smtp_sasl_mechanism_filter=plain,login

Revision as of 15:28, 28 April 2009

Overview

When you need to route all outgoing mail through your ISP's MTA, and that MTA requires that you authenticate, certain settings in postfix are required.

For this example, we will use mailrelay.example.com as the outgoing relay The authentication user will be username The password will be password

The outbound destination should be the canonical address. postfix will resolve CNAMEs to canonical addresses and then use that to lookup the username and password .


Godaddy example:

smtpout.secureserver.net is really smtp.starfieldtech.com, so make sure you enter smtp.starfieldtech.com

nslookup smtpout.secureserver.net
...
Non-authoritative answer:
smtpout.secureserver.net        canonical name = smtp.starfieldtech.com.
Name:   smtp.starfieldtech.com
Address: 64.202.165.58

Setting a relay host

Set the relay host in the admin console, MTA tab to point to your ISPs outgoing mail server. Your ISP can tell you the proper value for this.

You may have to set the port, as well. From the command line:

zmprov ms server.domain.com zimbraMtaRelayHost external.relay.com:#

Enabling SMTP authentication

Run all these commands as the zimbra user

Create a text file mapping which name/password should be used for each given outbound destination:

echo mailrelay.example.com username:password > /opt/zimbra/conf/relay_password

Create a postfix lookup table:

postmap hash:/opt/zimbra/conf/relay_password

Test that the lookup table is correct:

postmap -q mailrelay.example.com /opt/zimbra/conf/relay_password

This should return username:password.

postconf -e smtp_sasl_password_maps=hash:/opt/zimbra/conf/relay_password
postconf -e smtp_sasl_auth_enable=yes
postconf -e smtp_cname_overrides_servername=no

smtp_cname_overrides_servername=no is used because many smtp servers forward the connection different server than the one set in the smtp_sasl_password_maps file.

Example of the problem :

/opt/zimbra/conf/relay_password :

smtp.gmail.com username@gmail.com:password

but postfix connects to gmail-smtp.l.google.com

Postfix will not send the authentication info contained in smtp_sasl_password_maps file because it as no entry for the server gmail-smtp.l.google.com but has one for smtp.gmail.com

If you apply smtp_tls_per_site settings then smtp_cname_overrides_servername may become obsolete.

Restart postfix:

postfix reload

Enable TLS

As Zimbra user:

postconf -e smtp_use_tls=yes
postfix reload

Troubleshooting

After sending a test message, check the Log Files for the error:

(Authentication failed: cannot SASL authenticate to server ...: no mechanism available)

You can fix this problem by tweaking the auth mechanisms that postfix is willing to use. First check what auth mechanism postfix is configured to use - by default, you will see:

postconf smtp_sasl_security_options
smtp_sasl_security_options = noplaintext, noanonymous

Since noplaintext is present, postfix will refuse to use a mechanism that sends passwords in the clear. If your upstream relay host only supports PLAIN or LOGIN mechanisms (both of which send password in the clear), you have to remove noplaintext from smtp_sasl_security_options:

postconf -e smtp_sasl_security_options=noanonymous
postfix reload

If you are concerned about password-in-the-clear and your upstream relay host offers TLS, you might be interested in this smtp_use_tls variable.

See also [1].

Don't use brackets [] around the server name definition as seen in many places. Exp.:[smtp.gmail.com]


AT&T Yahoo DSL Specific

If outgoing mail is not being delivered and /var/log/mail.log shows:

(lost connection with smtp.att.yahoo.com while receiving the initial server greeting)

Some ISP's SMTP servers do not implement TLS properly on port 465 (AT&T Yahoo DSL in particular); mail clients handle this when making an SSL connection, however Postfix loses the server connection in this case. Port 587, the standard secondary SSL SMTP port, does work properly with TLS.

The proper commands for AT&T DSL customers in the above setup are:

Change:

zmprov ms server.domain.com zimbraMtaRelayHost external.relay.com:#

To:

zmprov ms server.domain.com zimbraMtaRelayHost smtp.att.yahoo.com:587

And add:

postconf -e smtp_sasl_mechanism_filter=plain,login
postconf -e smtp_sasl_security_options=noanonymous
postconf -e smtp_tls_security_level=may

With those changes the connection works properly. Source [2]

Persistence across Zimbra upgrades

I just did an upgrade of Zimbra 5.0.5 to 5.0.8 after doing the above - and all of the relay smtp auth changes stayed - they were not wiped out by the upgrade.

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