cute.ml

let is_valid ~email =
    match (String.length email, email) with
    | (0, _) -> Error "empty email is not valid"
    | (len, _) when len > max_email_length -> Error "Email length exceeds the limit"
    | (_, email) when string_is_bigger_than max_email_length [email] -> Error "Email is bigger than the limitations"
    | _ -> Ok ()

email.mli:

val max_recipient_length : int

val max_domain_length : int

val max_email_length : int

val validEmailRegex : Str.regexp

val string_is_bigger_than : int -> string list -> bool

(* val is_valid : email:string -> bool *)
val is_valid : email:string -> (unit, string) result