[Samba] Message subject rule to stick message to existing topic (some off-top) !

[CpServiceSPb .]

There is some, *may be*, off-top. If it is so, sorry.
What should I put to my e-mail subject that my outgoing message shoud be
sticked to either my or others existing topic ?
Should it be *Re: [Samba] Topic name* or *[Samba] Topic name* or simply *Topic
name* ?