@Asperamanca I have not used Outlook for years so I might be wrong but when you add sender to the address book you can select which message format is preferred from this sender only? This is per-client setting.
There was a bug in the login integration to Qt Account. This prevented new users from logging in, they got an internal server error.
Bug was fixed 26-Jun-2017 about 1 pm Finnish time. If you got the message, just try again now.
This is not the exact place to make a bug report, if this was your intension. You should check on JIRA and place a report there.
On the other hand, I had also already problems with editing of posts and replies. I could not reply nor add a new thread then. IN my case it was typically after an action on another webpage. This webpage had a problem with my browser (Chrome) and I had to use edge there. Apparently as a consequence of the initial trial on this webpage brought my browser into this state. Possibly you have had a similar issue earlier.
@chittaranjan Honestly, do you really think that someone will respond to such a posting? What are you trying to achive? What have you tried so far? What did you expect and what did you get instead? And: What is your question?