In biblical times, מלאך

referred either to someone sent to this world from above, or just to a regular messenger. Today, however, people use מלאך to speak of an angel only (or someone who behaves that way) – while שליח

 is a person carrying a message or a parcel.

For example:

הוא לא בדיוק מלאך.

He isn’t exactly an angel.

and

היא עובדת כשליחה בוולט.

She works as a delivery (driver) for Wolt.

Note that the feminine version of שליח is שליחה

. Likewise, a female angel is מלאכית

.