I've just upgraded from Kubuntu 15.04 to 15.10. Amongst many other annoyances, my KMail no longer loads any images in HTML emails, making it pretty much un-usable

Nothing's changed in the settings that I can see, and "Load External References is ticked. Is there anywhere else I should be looking?

Just to confirm, you didn't enable AdBlock in the settings, did you?

Nope... and I've hunted through all of the settings and couldn't really see anything else that could possibly be causing the issue.

One odd thing that I've noticed this morning is that sometimes you see the images load very briefly before being replaced with boxes and the normal "no entry" type symbol that you get when image loading is off. I.e. I think that it *is* loading the images, but then removing them almost immediately.

Can you check if in the Appearance > Message Window, "Gravatar support" is present, and if so, enabled?

"Enable Gravatar Support" is present but it isn't enabled.

I've now tried setting up a test user account and KMail still didn't display the images. However, I also tried setting up a VM with a fresh install of Kubuntu 15.10 and that did work ( sort of expected it to because otherwise everyone would be complaining. )

So, the upshot seems to be that it's something to do with the global set-up of the machine rather than any user settings... though I can't imagine what. Could there be some package missing or badly configured ( system wide config ) causing this?

I bit the bullet and re-installed Kubuntu 15.10 from scratch... KMail works fine now. Very odd - must have been a hangover from upgrading from 15.04 ( or even previous versions. )

I had the same problems as you with KMail not loading external references and also decided to install Kubuntu 15.10 on a new partition. This worked and I was reconfiguring the new install with all my previously installed packages which caused it to break again.

I was about to remove all the packages I'd installed yesterday when I wondered if it was something to do with the network settings I'd changed and it was.

In all previous versions of Kubuntu I'd set up a fixed IP address by modifying /etc/network/interfaces as below,

auto lo
iface lo inet loopback
address 127.0.0.1
netmask 255.0.0.0

# The primary network interface
iface eth0 inet static
dns-nameservers 192.168.2.1
address 192.168.2.102
netmask 255.255.255.0
gateway 192.168.2.1
auto eth0

In 15.10, it doesn't work and I've had to comment out everything related to eth0.

I'm wondering if this is breaking the loopback interface.

Ahh, now that's interesting. Previously I'd also set a static IP using the interfaces file... though in the mean time I'd added that static IP to my DHCP server so didn't bother doing the same on the re-install. It would explain why the issue doesn't seem very common.

I've no time to test atm, but it sounds pretty likely to be the cause. I'll set that as the answer ( can always un-set it if it turns out NOT to be the case. ) If it is, then it's most likely to be a Ubuntu issue rather than a KMail one.

I've mentioned the issue on the Kubuntu users mailing list and someone on there says that they've modified the interfaces file too without experiencing the issues I've been having. I'll need to do another fresh install and see what happens.

I have this issue too, and it does not go away if I revert /etc/network/interfaces to make my IP address dynamic, or static.

I have meet the same problem,but I using KMail 5.2.3. when I Enable Gravatar, It can load image, Thanks!

But I want to know,why cause this problem? When I print an email, I will see "please enable load external references", however when read the email in Kmail , I can't see this notice.