As nouns the difference between hailshot and mailshot
is that hailshot is small shot that scatters like hailstones while mailshot is bulk advertising sent through the post/mail.
As a verb mailshot is
to send bulk advertising to (somebody) in the post.
hailshot
English
Noun
(
-)
(obsolete) Small shot that scatters like hailstones.
- (Hayward)
(
Webster 1913)
mailshot
English
Verb
(mailshott)
To send bulk advertising to (somebody) in the post.