Thunderbird mail check problem fix to: "An error
occurred sending mail: Unable to establish a secure link with SMTP
server smtp.examplehost.com using STARTTLS since it doesn't
advertise that feature."
Some clients of one of the qmail servers mail domain complained
that there are problems sending e-mails with Thunderbird (pop /
imap) client.
The exact
Thunderbird sending error is:
Unable to establish a secure link with SMTP server
smtp.examplehost.com using STARTTLS since it doesn't advertise that
feature.
Switch off STARTTLS for that server or contact your service
provider.
For for almost half an hour I pondered why the heck this odd error
happens in sending mails with a fresh new Thunderbird (auto)
configured mail address.
Few months back some clients were experiencing similar STARTTLS
errors so I went back to check my previous post to get an idea
what was wrong then in order to determine if the current reported
error had to do with the previous one. My previous post is here -
How to work around STARTTLS Qmail Thunderbird / Outlook mail
sending (error) issues
After reading on the previous error and some assumptions I found
out the whole problem lays in incorrectly set DNS records.
By default Thunderbird (and probably other mail clients) are
configuring automatically as SMTP server (smtp.examplehost.com) if
the DNS record for smtp.examplehost.com points to an IP
address / host which belongs to another mail server, everytime
thunderbird tries to send email the incorrect smtp.examplehost.com
is used, hence the mail sending fails with the err:
Unable to establish a secure link with SMTP server
smtp.examplehost.com using STARTTLS since it doesn't advertise that
feature.
Switch off STARTTLS for that server or contact your service
provider.
In my case the DNS for examplehost.com which is the mail
server host was managed by Godaddy's DNS-es:
ns49.domaincontrol.com
ns50.domaincontrol.com
The A record for our domain smtp.examplehost.com was by
default set in GoDaddy to point to incorrect IP, so the fix was
simply to change the Domain alias of smtp.examplehost.com to the
proper mail host.
Another thing I had to do is change variables in
/var/qmail/supervise/qmail-smtpd/run and
/var/qmail/supervise/qmail-smtpdssl/run
In both files I changed variables:
SSL=0
ALLOW_INSECURE_AUTH=0
to
SSL=1
ALLOW_INSECURE_AUTH=1
Also variables FORCE_TLS and DENY_TLS in
/var/qmail/supervise/{qmail-smtpd,qmail-smtpdssl}/runshould
be:
FORCE_TLS=0
DENY_TLS=1
Though the problem was occuring in Mozilla Thunderbird, i'm sure
same email sending problem will be present if Microsoft Outlook
Express or any other desktop pop3 client is used.
After this changes I had to restart qmail server through
qmailctl:
# qmailctl stop; sleep 5; qmailctl start
This fixed clients mail sending issues ... hope this will help to
others looking for way to remove STARTTLS, TLS, SSL qmail
support ...