551675 - No fallback from IPv6 to IPv4 for dual-homed SMTP servers

Status: RESOLVED INCOMPLETE

(MailNews Core :: Networking: SMTP, defect)

Description

[Volker Stolz]

User-Agent:       Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_2; en-us) AppleWebKit/531.21.8 (KHTML, like Gecko) Version/4.0.4 Safari/531.21.10
Build Identifier: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3

Thunderbird does not seem to fall back from IPv6 to IPv4 for delivering mail. With limited/broken IPv6 connectivity telnet yields the following, while Thunderbird comes up with "The message could not be sent using SMTP server mail.foldr.org for an unknown reason."

[14:38:52]> telnet mail.foldr.org 587
Trying 2001:470:1f0b:15ba::1...
telnet: connect to address 2001:470:1f0b:15ba::1: Host is down
Trying 88.198.102.118...
Connected to mail.foldr.org.
Escape character is '^]'.
220 mail.foldr.org ESMTP Sendmail; Thu, 11 Mar 2010 14:39:03 +0100; (No UCE/UBE) logging access from: 1x-193-157-197-X.uio.no(OK)-1x-193-157-197-X.uio.no [193.157.197.X]
quit
221 2.0.0 mail.foldr.org closing connection

(Surprisingly, IMAP seems to do the right thing!)

Reproducible: Always

Steps to Reproduce:
1. "Break" IPv6 connectivty
2. Try to send mail
Actual Results:  
Thunderbird does not deliver email.

Expected Results:  
Firstly, Thunderbird should give a more exact error message. Secondly, it should probably try to fallback to IPv4.

Comment 1

[Wim Lewis]

I can confirm that this bug still exists in version 12.0.1 (Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:12.0) Gecko/20120428 Thunderbird/12.0.1). My experience is identical to Volker Stolz'.

I wonder if this is even an IPv6-specific bug, or if an SMTP server with two IPv4 addresses would exhibit the same bug if the first address is unreachable. (In which case it's a recurrence of bug 86917 perhaps?) Other old IPv6 bugs that look related: bug 108108, bug 136898.

Comment 2

[johann]

please see Bug 795113 which deals with two (2) aspects of IPv6 mailserver account problems for SM/TB. these apsects are addressed separately in the two (2) bugs, infra.

Bug 199391 seems to deal with the basic code problem in that IPv6 will not work for server accounts: sending via SMTP on (usually) 465 and collecting via IMAP on 143/993 -- i am familiar with both. it also claims that POP3 is equally affected, but i do not deal with this protocol.

Bug 551675 seems to indicate that the Bug 199391 problem (now going on 10 years old) does not offer an IPv4 fall-back after failing on the mozilla-preferred IPv6. one would conclude from this indication that DNS of the account's server name has an IPv4 MX in addition to the IPv6 (is multi-homed). this can be verified as demonstrated in Bug 795113.

hopefully, these bugs can be consolidated into Bug 795113 and someone will finally resolve all of the issues.

thank you,

Comment 3

[Ludovic Hirlimann [:Usul]]

Removing myslef on all the bugs I'm cced on. Please NI me if you need something on MailNews Core bugs from me.

Comment 5

[Wayne Mery (:wsmwk)]

Version 91 has all new smtp backend code. If you can still reproduce this issue, please file a new bug report https://bugzilla.mozilla.org/enter_bug.cgi?product=MailNews%20Core&component=Networking%3A%20SMTP