Fix issues with exim 4.94.x

Thanks @myvesta + @madeITBelgium for the fix 
Changes taken from  https://github.com/madeITBelgium/vesta/blob/master/install/os-configs/rhel/general/exim/exim.conf 
+ myvesta/vesta@1a6785e#diff-b0f6533e9ea0d44d31db3fd5c021ffb3acbbb7962bf77ec408d889715c84ba01

Author: jaapmarcus

bin/v-add-mail-account

@@ -72,6 +72,10 @@ if [[ "$MAIL_SYSTEM" =~ exim ]]; then
     echo $str >> $HOMEDIR/$user/conf/mail/$domain/passwd
 fi
 
+# Create mail account folder (mailbox)
+ mkdir $HOMEDIR/$user/mail/$domain/$account
+ chown $user:mail $HOMEDIR/$user/mail/$domain/$account
+ chmod 700 $HOMEDIR/$user/mail/$domain/$account
 
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 #                       Hestia                             #