They might be using scare tactics hoping you'll hand over the domain name without question. But I wonder if they have a case.
My suggestion would be to either A) ignore and see if they go away, and/or B) have a domain name lawyer send a reply showing you won't roll over. That's usually enough for parties like these to back down.
If you need a lawyer recommendation send me DM me on Twitter (@marckohlbrugge). More than happy to help.
FWIW, some people might mention a procedure called 'UDRP' which is typically used by TM owners to quickly and cheaply get a TM-infringing domain name. However, one of the requirements for a successful UDRP case is that the TM needs to have been issued BEFORE the domain name was registered. Which is not the case here. So a UDRP approach would fail for them.
The other way for them would indeed be to sue and try to claim TM infringement in court. I don't have much experience with TM law, so I'm not sure what your odds of winning are. But there might even be a way to get their TM invalidated.
TL;DR: Talk to a lawyer.
P.S.
If they have money for lawyers, they might also have money to buy your domain name. I wouldn't propose a purchase until you've talked to a lawyer (as it could hurt your case), but it's something to consider for later on.
Yes, although that criteria is somewhat subjective. Since an UDRP needs to meet all criteria, you can throw it out by just looking that the registration dates.
Note that I'm not a lawyer, but I've dealt with similar issues before through a qualified lawyer. Happy to introduce you. Not sharing name here publicly, because that could potentially be used against me. (i.e. someone intentionally creating a conflict of interest, etc)
My suggestion would be to either A) ignore and see if they go away, and/or B) have a domain name lawyer send a reply showing you won't roll over. That's usually enough for parties like these to back down.
If you need a lawyer recommendation send me DM me on Twitter (@marckohlbrugge). More than happy to help.
FWIW, some people might mention a procedure called 'UDRP' which is typically used by TM owners to quickly and cheaply get a TM-infringing domain name. However, one of the requirements for a successful UDRP case is that the TM needs to have been issued BEFORE the domain name was registered. Which is not the case here. So a UDRP approach would fail for them.
The other way for them would indeed be to sue and try to claim TM infringement in court. I don't have much experience with TM law, so I'm not sure what your odds of winning are. But there might even be a way to get their TM invalidated.
TL;DR: Talk to a lawyer.
P.S. If they have money for lawyers, they might also have money to buy your domain name. I wouldn't propose a purchase until you've talked to a lawyer (as it could hurt your case), but it's something to consider for later on.