As you have noticed there has been a recent change. The single click to activate has been replaced with more choices for control.

This came about because of requests by the public to make it easier to access and control this feature.

Previously this option only either showed remote once or added a check to an item in a contact's properties.

Now it offers to show remote in a single instance or add the email address to a list of exceptions. There is also the facility to edit those selections all accessible in one list and also the facility to switch off blocking of remote content' which is not adviseable, but the public did request that it must be made easier to do than via the Config Editor.

By creating the list of exceptions, it has also provided the ability to add a website and/or email addresses. So that if a website/company uses different email addresses depending upon who sent the messages, you can add the website (not sub domain) and it will then recognise and permit all the email addresses.

https://support.mozilla.org/en-US/kb/remote-content-in-messages

Previously, it was easier to single click, so quick and useful, but you did not have the control that is offered now. Single click was also easy to do by accident, so not so security concious. The blocking of remote content protects your privacy because spammers can verify your email address by detecting if you viewed a remote image in a message from them. Its also possible to embed an executable (malware) in images.

As this is not a bug, I cannot see the developers spending time on making any changes soon although you could make a request. https://bugzilla.mozilla.org/index.cgi?

I understand the need for greater flexibility to improve security. But think about what has been accomplished. Those that are not security conscious can just as easily click twice as they clicked once under the old version.

Almost every email today comes with HTML or images or something other than plain text. An experienced user can tell when a trusted contact's email address book has been copied (you get weird emails from your friends to buy junk). I never allowed remote content to be viewed by default, regardless if the sender was in my address book or not. I always decided to view on an email by email process. This has been replaced with a blanket, view all content. This seems less secure to me. I feel this click twice requirement does not improve security for those who always view remote content, and annoys and slows down those that have common sense. I would really like one button to click to view remote content. And preventing spammers from knowing an email address is valid via images does not hold much weight. Email addresses are bought and sold, there is so much junk email that filters are a necessity in this day and age. I get small comfort knowing I may have thwarted a spammer when I have to click twice every single time to read my emails.

I agree with everything dalejanus says. Almost every message these days has content other than plain text, and having to now make two clicks to show that content instead of the previous one, should not be needed.

Why can't there be two buttons? One as we had before to show the remote content. The other being the new one introduced recently to control remote content.

Update - Located some info which may be of interest to you. This bug report looks to be addressing the issue. changes to the 'Options' button which should not be a button but a drop down option and adapting to include a previous one click option. You could 'vote' fot the bug - located in the upper section -Importance

• https://bugzilla.mozilla.org/show_bug.cgi?id=1062961