Hi Alexandre,
Txs for you answers to every item 🙂
My turn to reply (I waited for 6.5 before replying and now I even installed 6.5.1 just to be sure and to avoid speaking about things which are maybe fixed in-between)
1/ Yes, I will send you the Credentials so that you can see for yourself. But I have just tested with 6.5.1 and I still see the same issue : I choose Acymailing's default template and everything seems fine until the last screen where the preview already show the bug in the html tag which is not correct (">)

2/ I always use Joomla, never ask me that question again 😃
And the Multilingual features are used natively (no external Extension, only core) and it works fine on the whole site.
3/ txs for the fix. I do confirm : everything's fine now 🙂
4/ do you mean it is now in 6.5.0 (or for which version will it be)
5/ sure. I must admin it is a bit specific to my site. But what is the Acymailing's file I should "override" in order to customize this myself (and remove any potential {index} with a regex of my own) ?
Suggestion 2/ : see the screenshot : I simply mean : as it is now the default values are "Yes" for "clickable title" and "0" for "truncate text after". It would be handy if Acymailing would remember the last choice (or to be able to set what you want by default) instead of having to change it every single time of your life 🙂
