See
https://bugs.contribs.org/show_bug.cgi?id=9384 for an explanation.
Stefano suggested to ask for possible alternatives. Even though I have around webmail 100 users and it would definitely be stressful to switch them to something else, installing SME 8.2 back and trying to backport all my data from 9.2 does not seem a very nice alternative.
My user base is not using any ohter Horde feature (calendar, shared contacts etc) except email.
However, the domain of the mail server is domainA.gr, meaning new web accounts are of the form user@domainA.gr. Since user accounts should have accounts of the form user@domainB.gr, from within Horde I configured each of the 100 user accounts (could possibly be done with scripting/MySQL, I know) to have that user@domainB.gr form.
The bottomline is that I am looking for maximum stability Horde alternatives, that have a user interface in Greek, can read the same mailboxes, can be configured to provide different email From: addresses permanently (ie not for one message, but for all), be admin friendly (not around 10000 dependencies, that might break SME) and be user friendly. With that order I guess.
From a nice chat I had with Stefano, roundcube comes as a possible alternative. Discuss pls.