The file.csv file content is :

user0001;password0001;user0002;password0002
user0011;password0011;user0012;password0012 ...

And the shell program is just :

{ while IFS=';' read u1 p1 u2 p2; do imapsync --user1 $u1 --password1
$p1 --user2 $u2 --password2 $p2 ... done ; } < file.csv

Better than the above while read loop is the use of Bash's builtin readarray as it allows to avoid spawning a sub-shell and therefore variable assignments from inside the loop work.