Recipients can be added in three ways:
addTo(): Adds a recipient to the mail with a "To" header
addCc(): Adds a recipient to the mail with a "Cc" header
addBcc(): Adds a recipient to the mail not visible in the header
getRecipients() serves list of the recipients.
clearRecipients() clears the list.
addCc() accept a second
optional parameter that is used as a human-readable name of the recipient for the
header. Double quotation is changed to single quotation and angle brackets to square
brackets in the parameter.
All three of these methods can also accept an array of email addresses
to add instead of one at a time. In the case of
addCc(), they can be associative arrays where the key is the
human readable name for the recipient.