I have a vague memory that this problem had already been discussed in the past and, if I'm not mistaken, the "conversation" view was not yet supported by SmarterMail at the time...
Gabriele Maoret - Head of SysAdmins at SERSIS
Currently manages 6 SmarterMail installations (1 in the cloud for SERSIS which provides services to a few hundred third-party email domains + 5 on-premise for customers who prefer to have their mail server in-house)