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After configuring a new Qmail+POP3+IMAP with vpopmail install based on Thibs QmailRocks I faced some issues with configuring mail accounts in Mozilla Thunderbird. The problem is also present in Microsoft Outlook Express as some colleagues working on Windows reported they can't configure there email accounts in Outlook either.

The issue was like this, the mail server is running fine, and I can send without issues directly from the server shell with mail command, however in Thunderbird I could only fetch the messages via POP3 or IMAP, whever I give a try to send one I got the error:

Sending of Message Failed
The message could not be sent using SMTP server for an
unknown reason. Please verify that SMTP server settings are correct and try
again, or contact your network administrator


Here is a screenshot preseting the issue, taken from my Thunderbird:

The reason for this error is an automatic setting that is being configured in Thunderbird in New Account Creation time:
Thunderbird queries the mail server and asks for the type of encryptions available for both POP3 and SMTP MX primary host.
Seeing that it supports STARTTLS data transfer encryption mail protocol for both POP3 / IMAP, Thunderbirds auto configuration does place STARTTLS to be used with SMTP and POP3

The incorrect setting which is being automatically filled in can be checked in following these Thunderbird menus:

Edit -> Account Settings -> Outgoing Server (SMTP)


If the configured mail account MX server is let's say mail.exampledomain.com one needs to Edit the settings for this SMTP auto configured domains and he will see some example settings like the one shown in the below screenshot:

You can see from above's screenshot that the auto configured Connection Security setting is improperly set to: STARTTLS. Usually STARTTLS should be working on SMTP port 25, however it seems the problem consists in the fact that the MAIL FROM and RCPT TO is sent in incorrec time (ain't sure if its before or after the encryption).

Therefore the consequence of this failure to use STARTTLS being detected as the correct encryption type for SMTP lead that the new configured mail server clients were unable tot properly connect and send emails via the SMTP listening server on port 25.

I give a try and changing the Connection Security:STARTTLS to Connection SecuritySSL/TLS immediately resolved the SMTP sending issues. Therefore as I found out the SMTP server is working just fine configured to use my QMAIL on port 465 with Connection Security: SSL/TLS and hence to work around the SMTP sending issues, decided to completely disable the STARTTLS encryption to be reported as a supported encryption by qmail-smtpd

On Thibs QmailRocks and some other Qmail installstions based more or less on qmail.jms1.net service damemontools scripts, this can be done by simply changing a line:

DENY_TLS=0


to

DENY_TLS=1


The qmail start up scripts which these change has to be done if one has configured a mail server based on QmailRocks Thibs updated tutorial are:

1. /service/qmail-smtpd
2. /service/qmail-smtpdssl

A quick way to do the DENY_TLS=0 to DENY_TLS=1 changes via sed is like this:

qmail# sed -e 's#DENY_TLS=0#DENY_TLS=1#g' /service/qmail-smtpd/run >> /tmp/qmail-smtpd-run;qmail# sed -e 's#DENY_TLS=0#DENY_TLS=1#g' /service/qmail-smtpdssl/run >> /tmp/qmail-smtpdssl-run;qmail# mv /tmp/qmail-smtpd-run /service/qmail-smtpd/run
qmail# mv /tmp/qmail-smtpdssl-run /service/qmail-smtpdssl/run


After the correct modifications, of course as usual a qmail restart is required, e.g.:

qmail# qmailctl restart
...


Making this changes, irradicated the sending issues. It's best practice that the account which had issues with sending before is deleted and recreated from scratch.
Hope this helps somebody out there who encounters the same issue. Cheers

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This entry was posted on Wednesday, October 26th, 2011 at 10:15 pm and is filed under FreeBSD, Linux, Qmail, System Administration, Various, Web and CMS. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.