If you use a Domain, Logo, or mark to sell or promote yourself or a tangible product or brand then you have every right to defend it as your trademark.
Timeline.
On Monday you buy domainname.com, you offer goods or services either free or payed and 1 second after you launch the domain you can defend it against trademark violation were someone to register a similar domain or service the next day.
However its never that clean cut.. too many variables to consider.. but bottom line, a trademark does not need to be registered it just needs to be a mark that distinquishes you in trade, hence the name TRADE MARK