using user@domain.tld instead user.domain.tld

hello all, few hours i migrated a friend's plesk site to my virtualmin site. in plesk the users had usernames like user@domain.tld in virtualmin users have usernames like user.domain

my friend has several clients (smartphones, thunderbird, outlook) that uses the user@domain.tld scheme, so i decided to change it for this domain..

First change was: Virtualmin/Server templates/Default Settings/Mail for Domain/Format for usernames that include domain/username@domain Second, i went to: Virtualmin/Server configuration/Change Domain Name/Change user name suffix and group? = Change to domain.tld

i added 2 users, and everything seemed fine. but old users could not receive mail.. then i noticed that for every new user there was a double line in /etc/passwd gmich@eco-bros.gr:x:1082:1032::/home/eco-bros.gr/homes/gmich:/dev/null gmich-eco-bros.gr:x:1082:1032::/home/eco-bros.gr/homes/gmich:/dev/null

the same happened in /etc/shadow gmich@eco-bros.gr:$6$1170....j1RR6.:17496:::::: gmich-eco-bros.gr:$6$11708....dVtj1RR6.:17496::::::

so for every user, added one line, in both files, replacing @ with -

next step was to add one line per user in /etc/postfix/virtual, for example: gmich1@eco-bros.gr gmich1-eco-bros.gr gmich@eco-bros.gr gmich-eco-bros.gr

now, all users get mail.. and they can login and read/send via roundcube

my problem is that i cannot make Thunderbird to work.. username gmich@eco-bros.gr is not working...

any suggestions?