This is a message from the "IRS" saying they are filing suit against you and a warrant has been issued for your arrest. They offer no information, or even use a name. They want you to give them all the information "to check against their  records".  As soon as you question them they disconnect.  Absolute scam! If IRS wants to get in touch with you they use the mail. Don't bother answering them if they call. Scum bags!