Suspected malicious communications.
I’m not sure which category they think it falls under:
(a)a letter or other article which conveys—
(i)a message which is indecent or grossly offensive;
(ii)a threat; or
(iii)information which is false and known or believed to be false by the sender; or
(b)any other article which is, in whole or part, of an indecent or grossly offensive nature,