I use Kontact 4.13.3.

I just discovered in the 1. tab "contact" on the bottom right a "message"-section. There are two options: display messages as standard, plan text or html and contend from remote server accepts with html.

What's that? How does it work?

I understand that you are talking about when you open a contact card in the application Kaddressbook in the suite Kontact, no?
That section configures Kmail messages for said contact. The default is that Kmail loads the mails you receive in plain text, with no format, but if you choose HTML then you will see that contact's email messages with format, colors, columns, etc, in case said contact has sent you a HTML message, of course.
Allowing content from remote server loads the inserted files that the formated email (HTML) could have, for example, images.
This is not recommended unless you trust in the contact you are allowing HTML and especially remote content. Plain text does nothing, HTML and remote content can reveal that you have opened the message, which is perfect to make spammers' lifes easier.

Correct: in fact, most spammers will use images in email as proof of the existence of your address, to bomb you even further.

Thanks for the explanation!

Yes, that's what I meant. Currently I use KMail, Kaddressbook and KOrganizer in the Kontact-suit, that's works fine. Normally mail with plain text and HTML only from trusted senders, if plain text isn't readable. KMail uses the mail-addresses from KOrganizer.

Did I get it right that I can display the mail within the active contact in Kaddressbook? How? At the moment I copy the address and start a search in KMail, that works but is rather inconvenient.

wired2051 wrote:Did I get it right that I can display the mail within the active contact in Kaddressbook? How? At the moment I copy the address and start a search in KMail, that works but is rather inconvenient.

I'm not sure if I understand you well. You are asking if you can display the mail messages within each contact's Kaddressbook cards, in some section or tab, but always inside the contact's card? If that's what you meant, I thknk that the answer is no. Kaddressbook only displays the info of your contacts, as far as I know, but not what they write to you, for that purpose you must use Kmail. And the «Messages» section only configures how you will see the selected contact's messages in Kmail.
If you want to see the mails from a determinate contact in Kmail you can filter the messages in your mail folders typing the first letters of that contact's name, address or any other datum you have in said contact's card in Kaddressbook; or, as you said, you can do a search, and save it with your contact's name, for example. It will be alwas accesible in the folder list, at the very bottom.

Appendix
«You can create a virtual folder with search parameters by going to either Edit → Find Messages..., Tools → Find Messages..., or Keyboard shortcut S. Enter your search parameters into the dialog. Name your search at the bottom Search folder name: textbox, e.g. emails with the word Blog. Click the Search button. Now select the Open Search Folder button. Your results folder will be at the bottom of the Folder pane.»
Read it complete here, in the paragraph «Creating and Using Folders».

Anyway, I like the idea of being able to see all the emails of a contact from Kaddressbook, vía some link to Kmail or something like that. Perhaps you could send a feature request to Kmail's developers.

eemantsal wrote:And the «Messages» section only configures how you will see the selected contact's messages in Kmail.

I thought I define how HTML is handled in KMail in Preferences > KMail > safety > prefer HTML to plain text (I've not activated) and in Preferences > KMail > editor > answer and forwarding with HTML if possible (I've not activated). But now, I made some tests and it's true, you can define for each contact if the messages are shown in KMail with HTML or not. Amazing - but understandable, so you can define your own "trusted sources". So I learned something new. Thanks!

eemantsal wrote:If you want to see the mails from a determinate contact in Kmail you can filter the messages in your mail folders typing the first letters of that contact's name, address or any other datum you have in said contact's card in Kaddressbook; or, as you said, you can do a search, and save it with your contact's name, for example. It will be alwas accesible in the folder list, at the very bottom.

That's what I know and already use:

• filter messages of the opened folder by typing in upper text-box <alt-q>
• searching messages in several folders with several options <s>
• search in message-text <ctrl+f>

eemantsal wrote:Anyway, I like the idea of being able to see all the emails of a contact from Kaddressbook, vía some link to Kmail or something like that. Perhaps you could send a feature request to Kmail's developers.

Where do I have to make the wish?
I think that's no great deal: it's only a search for the actual mail in from and to... Probably it's already suggested but not approved.

wired2051 wrote:Where do I have to make the wish?
I think that's no great deal: it's only a search for the actual mail in from and to... Probably it's already suggested but not approved.

The place is bugs.kde.org. You can search if your ideas has already been requested here and if it's already there, you can comment to suport it. The more people requests it, I suppose the more the attentaion developers will pay to it. But you are right: many often developers don't have the time to solve all bugs and feature requests even if they like them. But if users don't try we'll never know.