Send your letter by email and it arrives practically instantaneously.
Send it by ‘snail mail’ and it’s going to take a day or more at least, as it wends its way through the postal system.
Clever phrase. Neat little rhyme with a nice derogatory tone.
One observation though: it belongs to the English language.
I say this because the Italian for the @ sign, integral to email addresses, is ‘chiocciola’ which means snail.
Because it looks like a snail.