Recipients can be added in three ways:
addTo(): Adds a recipient to the mail with a "To" header
addTo()
addCc(): Adds a recipient to the mail with a "Cc" header
addCc()
addBcc(): Adds a recipient to the mail not visible in the header.
addBcc()
addTo() and addCc() accept a second optional parameter that is used as a human-readable name of the recipient for the header.