I raised this problem before a while ago in the Zarafa WebApp forum, and was told is would be fixed by the new editor in Kopano… But it is still a problem.
To recap - the problem is that sometimes (not always) when copying and pasting data from a HTML source into a mail, the text looks perfectly fine when sending, but when it is received by the recipient, it is illegible.
The problem seems to be that hidden HTML code that embeds itself and/or missing CSS stuff… regarless the end result is that all the text is displayed on top of itself rendering it unreadable.
However, looking at the email as text or via z-push is fine.
The way around the problem is to copy and paste it into notepad first to remove the pormating, but is there a way this can be fixed directly in WebApp?