An alternative valediction for sailors to “fair winds”
Calm sea and a prosperous voyage
This is a well-known alternative to the phrases cited by the poster, and is the English language title of the orchestral concert overture op. 27 by Felix Mendelssohn — German title Meeresstille und glückliche Fahrt.
It has the advantage that you could attach a link to the music in an email, apparently free here, although I prefer to reward artists by buying their products.
May the wind always be at your back (and the sun warm upon your face)
...is an Irish blessing for sailors.