1 /* $NetBSD: smtputf8.h,v 1.4 2025/02/25 19:15:46 christos Exp $ */ 2 3 #ifndef _SMTPUTF8_H_INCLUDED_ 4 #define _SMTPUTF8_H_INCLUDED_ 5 6 /*++ 7 /* NAME 8 /* smtputf8 3h 9 /* SUMMARY 10 /* SMTPUTF8 support 11 /* SYNOPSIS 12 /* #include <smtputf8.h> 13 /* DESCRIPTION 14 /* .nf 15 16 /* 17 * Global library. 18 */ 19 #include <sendopts.h> 20 21 /* 22 * Avoiding chicken-and-egg problems during the initial SMTPUTF8 roll-out in 23 * environments with pre-existing mail flows that contain UTF8. 24 * 25 * Prior to SMTPUTF8, mail flows that contain UTF8 worked because the vast 26 * majority of MTAs is perfectly capable of handling UTF8 in address 27 * localparts (and in headers), even if pre-SMTPUTF8 standards do not 28 * support this practice. 29 * 30 * When turning on Postfix SMTPUTF8 support for the first time, we don't want 31 * to suddenly break pre-existing mail flows that contain UTF8 because 1) a 32 * client does not request SMTPUTF8 support, and because 2) a down-stream 33 * MTA does not announce SMTPUTF8 support. 34 * 35 * While 1) is easy enough to avoid (keep accepting UTF8 in address localparts 36 * just like Postfix has always done), 2) presents a thornier problem. The 37 * root cause of that problem is the need for SMTPUTF8 autodetection. 38 * 39 * What is SMTPUTF8 autodetection? Postfix cannot rely solely on the sender's 40 * declaration that a message requires SMTPUTF8 support, because UTF8 may be 41 * introduced during local processing (for example, the client hostname in 42 * Postfix's Received: header, adding @$myorigin or .$mydomain to an 43 * incomplete address, address rewriting, alias expansion, automatic BCC 44 * recipients, local forwarding, and changes made by header checks or Milter 45 * applications). 46 * 47 * In summary, after local processing has happened, Postfix may decide that a 48 * message requires SMTPUTF8 support, even when that message initially did 49 * not require SMTPUTF8 support. This could make the message undeliverable 50 * to destinations that do not support SMTPUTF8. In an environment with 51 * pre-existing mail flows that contain UTF8, we want to avoid disrupting 52 * those mail flows when rolling out SMTPUTF8 support. 53 * 54 * For the vast majority of sites, the simplest solution is to autodetect 55 * SMTPUTF8 support only for Postfix sendmail command-line submissions, at 56 * least as long as SMTPUTF8 support has not yet achieved wold domination. 57 * 58 * However, sites that add UTF8 content via local processing (see above) should 59 * autodetect SMTPUTF8 support for all email. 60 * 61 * smtputf8_autodetect() uses the setting of the smtputf8_autodetect_classes 62 * parameter, and the mail source classes defined in mail_params.h. 63 */ 64 extern int smtputf8_autodetect(int); 65 66 /* 67 * The flag SMTPUTF8_FLAG_REQUESTED is raised on request by the sender, or 68 * when SMTPUTF8 auto-detection is enabled and a queue file contains at 69 * least one UTF8 envelope sender, envelope recipient, or message header. 70 * Once this flag is raised, it is preserved when mail is forwarded or 71 * bounced. 72 * 73 * The flag SMTPUTF8_FLAG_HEADER is raised when a queue file contains at least 74 * one UTF8 message header even if SMTPUTF8_FLAG_REQUESTED is disabled. 75 * 76 * The flag SMTPUTF8_FLAG_SENDER is raised when a queue file contains an UTF8 77 * envelope sender, even if SMTPUTF8_FLAG_REQUESTED is disabled. 78 * 79 * The three flags SMTPUTF8_FLAG_REQUESTED/HEADER/SENDER are stored in the 80 * queue file, are sent with delivery requests to Postfix delivery agents, 81 * and are sent with "flush" requests to the bounce daemon to ensure that 82 * the resulting notification message will have a content-transfer-encoding 83 * of 8bit. The derived flags SMTPUTF8_FLAG_HEADER/SENDER are ignored when a 84 * message is re-queued with "postsuper -r". They may be regenerated by the 85 * cleanup daemon. 86 * 87 * In the future, mailing lists will have a mix of UTF8 and non-UTF8 88 * subscribers. With the following flag, Postfix can avoid requiring 89 * SMTPUTF8 delivery when it isn't really needed. 90 * 91 * The fourth flag, SMTPUTF8_FLAG_RECIPIENT, is raised when a delivery request 92 * (NOT: message) contains at least one UTF8 envelope recipient. This flag 93 * is NOT stored in the queue file. The flag is used ONLY in requests to 94 * Postfix delivery agents, to give delivery agents flexibility when 95 * delivering messages to non-SMTPUTF8 servers. Delivery agents may then 96 * pass the flag to the bounce daemon. 97 * 98 * If a delivery request has none of the flags SMTPUTF8_FLAG_RECIPIENT, 99 * SMTPUTF8_FLAG_SENDER, or SMTPUTF8_FLAG_HEADER, then the message can 100 * safely be delivered to a non-SMTPUTF8 server (DSN original recipients 101 * will be encoded appropriately per RFC 6533). 102 * 103 * To allow even more SMTPUTF8 mail to be sent to non-SMTPUTF8 servers, 104 * implement RFC 2047 header encoding in the Postfix SMTP client, and update 105 * the SMTP client protocol engine. 106 */ 107 #define SMTPUTF8_FLAG_NONE (0) 108 /* In queue file, delivery request, or bounce request. */ 109 #define SMTPUTF8_FLAG_REQUESTED SOPT_SMTPUTF8_REQUESTED 110 #define SMTPUTF8_FLAG_HEADER SOPT_SMTPUTF8_HEADER 111 #define SMTPUTF8_FLAG_SENDER SOPT_SMTPUTF8_SENDER 112 /* In delivery or bounce request only. */ 113 #define SMTPUTF8_FLAG_RECIPIENT SOPT_SMTPUTF8_RECIPIENT 114 115 #define SMTPUTF8_FLAG_ALL SOPT_SMTPUTF8_ALL 116 #define SMTPUTF8_FLAG_DERIVED SOPT_SMTPUTF8_DERIVED 117 118 /* LICENSE 119 /* .ad 120 /* .fi 121 /* The Secure Mailer license must be distributed with this software. 122 /* AUTHOR(S) 123 /* Wietse Venema 124 /* IBM T.J. Watson Research 125 /* P.O. Box 704 126 /* Yorktown Heights, NY 10598, USA 127 /* 128 /* Wietse Venema 129 /* porcupine.org 130 /*--*/ 131 132 #endif 133
Indexes created Tue Aug 11 00:25:38 UTC 2026