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