Q. May one write a greeting on Tisha Bav, such as to write good afternoon in an email or to text good morning to his nonreligious mother?
Can one answer an email from a non-observant, or a Gentile with a greeting, since otherwise it would seem insulting or offensive?
A. Shulchan Aruch (O.H. 554: 20) rules that one should not greet another on Tisha Beav. However if someone ignorant of this ruling greeted, he may answer back in a slow and serious tone, so as not to embarrass the greeter.
Horav Shlomo Miller’s Shlit’a opinion is that one may express a general wish to all, such as let there be health or peace in the world and similar.
One can also mention in an answer that since this is our greatest day of mourning, he wishes everyone consolation and future happiness.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a