Hi,
I want to install roundcube because lets be honest the default usermin doens’t have much functions.
Is there a guide on how to install this (once) so that every domain has access to it?
Best regards
Jordy
Please FORUM RULES and then you find to use search first. 
While there should be a plugin and lot of info’s as i rembember according roundcube.
Also for other questions first: Forum Rules, reading DOCU"S , WIKI’s then forum and/or websearch, …
And in forum rules is ofcourse also you have to post Software versions and so on if asking for support.
If you’re a newbie then here https://www.virtualmin.com/forum/281 there is also the link for forumguidelines
Oke, will have a look, thx