Mass. Gen. Laws ch. 234A § 19
At least twelve weeks prior to the commencement of any term of grand or trial juror service, the office of jury commissioner shall summon by first-class mail, grand and trial jurors from the corresponding master juror list to appear for juror service within each judicial district. The summons shall state whether the anticipated service is that of a grand or trial juror, the beginning date of the term; the name, address, hour and room number, if any, of the courthouse or office to which the juror is directed to report on the first day of service; the fact that a trial juror has the right to one postponement of his term of juror service for not more than one year; the fact that a knowing failure to obey the summons without justifiable excuse is a crime, which, upon conviction, may be punished by fine of not more than two thousand dollars; and such other information and instructions as are deemed appropriate by the jury commissioner. The jury commissioner may use a postcard summons for purposes of summoning grand and trial jurors. A postcard summons shall be considered an official juror summons for purposes of this chapter.
Mass. Gen. Laws ch. 234A, § 19