It was in 1971 that Ray Tomlinson saw the “at sign” and thought it could be good to append the mail server host to the name of the person receiving an email. He describes this decision:
“I chose to append an at sign and the host name to the user’s (login) name. I am frequently asked why I chose the at sign, but the at sign just makes sense. The purpose of the at sign (in English) was to indicate a unit price (for example, 10 items @ $1.95). I used the at sign to indicate that the user was “at” some other host rather than being local.”
While there is some debate about the true origin of the @, the earliest found use dates back almost 500 years to May 4, 1536 when Florentine merchant Francesco Lapi used the symbol twice in a letter, first in the date and again as a unit of volume measure. Back then, he was using @ as short hand for the Italian word “amphora” (in Spanish, it is “arroba”) which was a terra cotta jar used to carry wine, oil, spices, or grain.