Thomas Ludwig Reporter
	Description • 6 years ago

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko
Build ID: 20100101

Steps to reproduce:

I used the site https://www.emailprivacytester.com/  with several test emails displayed as plain text, simplified HTML and HTML.

in about:config I had the following settings:

network.dns.disablePrefetch;true
network.prefetch-next;false

In the HTML mails any remote content was forbidden.


Actual results:

When using plain text and simplified HTML, all tests on that site failed as expected.

When using HTML mails, the following two tests were triggered:

DNS Prefetch - Link
DNS Prefetch - Anchor


Expected results:

As no remote content was allowed and dns prefetch was explicitly forbidden, all tests on that site should have failed.

	Wayne Mery (:wsmwk)
	Comment 1 • 6 years ago

Fails also for me using v60 on windows

http://kb.mozillazine.org/Network.dns.disablePrefetch

	Magnus Melin [:mkmelin]
	Comment 2 • 6 years ago

All tests seem ok (remain gray) for me on linux, both with 60 and trunk.

	Thomas Ludwig Reporter
	Comment 3 • 6 years ago

I'm actually also on Linux (I had used the User-Agent Switcher add-on in Firefox). I just repeated the test with a fresh Firefox profile and can confirm the findings in my 1st post.

Magnus, if the tests for you were okay although my findings were confirmed by Wayne, this suggests that there seems to be, at least, an inconsistent behaviour in Thunderbird.

Btw: What is actually the intended behaviour in TB? IMO, even without those settings in about:config, DNS prefetch should never be done in email clients for privacy reasons.

	Magnus Melin [:mkmelin]
	Comment 4 • 6 years ago

No it's not intended to do DNS prefetch. 

(I'll note network.prefetch-next, is true by default, but still with that on, nothing turns red for me.)

	Jorg K (CEST = GMT+2)
	Comment 5 • 6 years ago

I set network.dns.disablePrefetch to true and ran the test and DNS Prefetch Anchor and Link came back red. That's on Windows 10.