Standards, Environments, and Macros envelopes(5) NNNNAAAAMMMMEEEE envelopes - sender/recipient lists attached to messages IIIINNNNTTTTRRRROOOODDDDUUUUCCCCTTTTIIIIOOOONNNN Electronic mail messages are delivered in _e_n_v_e_l_o_p_e_s. An envelope lists a _s_e_n_d_e_r and one or more _r_e_c_i_p_i_e_n_t_s. Usu- ally these envelope addresses are the same as the addresses listed in the message header: (envelope) from djb to root From: djb To: root In more complicated situations, though, the envelope addresses may differ from the header addresses. EEEENNNNVVVVEEEELLLLOOOOPPPPEEEE EEEEXXXXAAAAMMMMPPPPLLLLEEEESSSS When a message is delivered to several people at different locations, it is first photocopied and placed into several envelopes: (envelope) from djb to root From: djb Copy #1 of message To: root, god@brl.mil (envelope) from djb to god@brl.mil From: djb Copy #2 of message To: root, god@brl.mil When a message is delivered to several people at the same location, the sender doesn't have to photocopy it. He can instead stuff it into one envelope with several addresses; the recipients will make the photocopy: (envelope) from djb to god@brl.mil, angel@brl.mil From: djb To: god@brl.mil, angel@brl.mil, joe, frde Bounced mail is sent back to the envelope sender address. The bounced mail doesn't list an envelope sender, so bounce loops are impossible: (envelope) from <> to djb From: MAILER-DAEMON To: djb Subject: unknown user frde The recipient of a message may make another copy and forward it in a new envelope: (envelope) from djb to joe SunOS 5.11 Last change: 1 Standards, Environments, and Macros envelopes(5) From: djb Original message To: joe (envelope) from joe to fred From: djb Forwarded message To: joe A mailing list works almost the same way: (envelope) from djb to sos-list From: djb Original message To: sos-list (envelope) from sos-owner to god@brl.mil From: djb Forwarded message To: sos-list to recipient #1 (envelope) from sos-owner to frde From: djb Forwarded message To: sos-list to recipient #2 Notice that the mailing list is set up to replace the envelope sender with something new, ssssoooossss----oooowwwwnnnneeeerrrr. So bounces will come back to ssssoooossss----oooowwwwnnnneeeerrrr: (envelope) from <> to sos-owner From: MAILER-DAEMON To: sos-owner Subject: unknown user frde It's a good idea to set up an extra address, ssssoooossss----oooowwwwnnnneeeerrrr, like this: the original envelope sender (ddddjjjjbbbb) has no way to fix bad ssssoooossss----lllliiiisssstttt addresses, and of course bounces must not be sent to ssssoooossss----lllliiiisssstttt itself. HHHHOOOOWWWW EEEENNNNVVVVEEEELLLLOOOOPPPPEEEE AAAADDDDDDDDRRRREEEESSSSSSSSEEEESSSS AAAARRRREEEE SSSSTTTTOOOORRRREEEEDDDD Envelope sender and envelope recipient addresses are transmitted and recorded in several ways. When a user injects mail through qqqqmmmmaaaaiiiillll----iiiinnnnjjjjeeeecccctttt, he can supply a RRRReeeettttuuuurrrrnnnn----PPPPaaaatttthhhh line or a -ffff option for the envelope sender; by default the envelope sender is his login name. The envelope recipient addresses can be taken from the command line or from various header fields, depending on the options to qqqqmmmmaaaaiiiillll----iiiinnnnjjjjeeeecccctttt. Similar comments apply to sssseeeennnnddddmmmmaaaaiiiillll. When a message is transferred from one machine to another through SMTP, the envelope sender is given in a MMMMAAAAIIIILLLL FFFFRRRROOOOMMMM command, the envelope recipients are given in RRRRCCCCPPPPTTTT TTTTOOOO com- mands, and the message is supplied separately by a DDDDAAAATTTTAAAA com- mand. SunOS 5.11 Last change: 2 Standards, Environments, and Macros envelopes(5) When a message is delivered by qqqqmmmmaaaaiiiillll to a single local reci- pient, qqqqmmmmaaaaiiiillll----llllooooccccaaaallll records the recipient in DDDDeeeelllliiiivvvveeeerrrreeeedddd----TTTToooo and the envelope sender in RRRReeeettttuuuurrrrnnnn----PPPPaaaatttthhhh. It uses DDDDeeeelllliiiivvvveeeerrrreeeedddd----TTTToooo to detect mail forwarding loops. sssseeeennnnddddmmmmaaaaiiiillll normally records the envelope sender in RRRReeeettttuuuurrrrnnnn---- PPPPaaaatttthhhh. It does not record envelope recipient addresses, on the theory that they are redundant: you received the mail, so you must have been one of the envelope recipients. Note that, if the header doesn't have any recipient addresses, sssseeeennnnddddmmmmaaaaiiiillll will move envelope recipient addresses back into the header. This situation occurs if all addresses were originally listed as BBBBcccccccc, since BBBBcccccccc is automatically removed. When sssseeeennnnddddmmmmaaaaiiiillll sees this, it creates a new AAAAppppppppaaaarrrreeeennnnttttllllyyyy----TTTToooo header field with the envelope recipient addresses. This has the strange effect that each blind- carbon-copy recipient will see a list of all recipients on the same machine. When a message is stored in mmmmbbbbooooxxxx format, the envelope sender is recorded at the top of the message as a UUCP-style FFFFrrrroooommmm (no colon) line. Note that this line is less reliable than the RRRReeeettttuuuurrrrnnnn----PPPPaaaatttthhhh line added by qqqqmmmmaaaaiiiillll----llllooooccccaaaallll or sssseeeennnnddddmmmmaaaaiiiillll. SSSSEEEEEEEE AAAALLLLSSSSOOOO qmail-header(5), qmail-local(8), qmail-inject(8) SunOS 5.11 Last change: 3