I am a DBA in Connecticut a suit was filed against me in Mass. is this legal Ihave a warehouse there

You don't say what the suit is about, or whether you own the warehouse, each of which could be an important factor.  You also don't say what other contacts, if any, you have with Mass. An court from a state in which you don't reside can get jurisdiction over you if you have "minimum contacts" with the state so that it is not considered unfair to sue you there.  Generally, owning real property in a state is sufficient so that you can be sued there, so if you own the Mass. warehouse, you can probably be sued there. Also, the contacts needed to confer jurisdiction are less if the dispute arises from those contacts than if they are unrelated.  Thus, for example, sending one letter to Mass. in the past  year is probably not enough of a contact, by itself, to allow a Massachusetts court to exercise jurisdiction over you, but if the suit is over what you wrote in that letter it probably is sufficient. Assuming that you don't own the warehouse, other factors which could be important to an analysis of whether you can be sued in Mass.  include whether you ever visit the state, and if so how often and for how long, whether you advertise in Mass., whether you own any personal property in the state (like a car registered or stored in Mass., or stock in a Mass. corporation), etc. Even if you don't believe the Court has jurisdiction over you, you should not ignore the lawsuit.  You should at least make a motion to dismiss based on lack of jurisdiction.  If you ignore the suit, a default judgment will likely be entered against you.  If so, the plaintiff will seek to collect on that judgment in Ct., and your only defense will be that the Court lacked jurisdiction.  If it is found that the Mass. court did  have jurisdiction, you will have lost.   You will not, at that late date, have the opportunity to litigate any other defenses you might have.