The Resent-Sender field inherits resent-sender StructuredField and handles the Resent-Sender: header field in the email.
Sending resent_sender to a mail message will instantiate a Mail::Field object that has a ResentSenderField as its field type. This includes all Mail::CommonAddress module instance metods.
Only one Resent-Sender field can appear in a header, though it can have multiple addresses and groups of addresses.
mail = Mail.new mail.resent_sender = 'Mikel Lindsaar <mikel@test.lindsaar.net>, ada@test.lindsaar.net' mail.resent_sender #=> ['mikel@test.lindsaar.net'] mail[:resent_sender] #=> '#<Mail::Field:0x180e5e8 @field=#<Mail::ResentSenderField:0x180e1c4 mail['resent-sender'] #=> '#<Mail::Field:0x180e5e8 @field=#<Mail::ResentSenderField:0x180e1c4 mail['Resent-Sender'] #=> '#<Mail::Field:0x180e5e8 @field=#<Mail::ResentSenderField:0x180e1c4 mail.resent_sender.to_s #=> 'Mikel Lindsaar <mikel@test.lindsaar.net>, ada@test.lindsaar.net' mail.resent_sender.addresses #=> ['mikel@test.lindsaar.net', 'ada@test.lindsaar.net'] mail.resent_sender.formatted #=> ['Mikel Lindsaar <mikel@test.lindsaar.net>', 'ada@test.lindsaar.net']