sed - Bash read line and clone it -

ok, i've many files have structure:

mail1@mail.it mail2@mail.com mail3@mail.co.uk 

now i'm trying convert files, have results

mail1@mail.it;mail1@mail.it mail2@mail.com;mail2@mail.com mail3@mail.co.uk;mail3@mail.co.uk 

this because i've import file create mailing list, @ every line need have return in windows style.

i tried to sed don't know, , don't have found not in days

i tried approach:

sed 's/^/;/' input.txt > output.txt 

but miss how "clone" content of each line, idea pretty simple read line , paste ; @ end, result must right.

any ideas how replicate content of each line?

j

awk '{print $0";"$0}' file 

output:

 mail1@mail.it;mail1@mail.it mail2@mail.com;mail2@mail.com mail3@mail.co.uk;mail3@mail.co.uk