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Diffstat (limited to 'src/global/smtputf8.h')
| -rw-r--r-- | src/global/smtputf8.h | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/src/global/smtputf8.h b/src/global/smtputf8.h new file mode 100644 index 0000000..95d6583 --- /dev/null +++ b/src/global/smtputf8.h @@ -0,0 +1,113 @@ +#ifndef _SMTPUTF8_H_INCLUDED_ +#define _SMTPUTF8_H_INCLUDED_ + +/*++ +/* NAME +/* smtputf8 3h +/* SUMMARY +/* SMTPUTF8 support +/* SYNOPSIS +/* #include <smtputf8.h> +/* DESCRIPTION +/* .nf + + /* + * Avoiding chicken-and-egg problems during the initial SMTPUTF8 roll-out in + * environments with pre-existing mail flows that contain UTF8. + * + * Prior to SMTPUTF8, mail flows that contain UTF8 worked because the vast + * majority of MTAs is perfectly capable of handling UTF8 in address + * localparts (and in headers), even if pre-SMTPUTF8 standards do not + * support this practice. + * + * When turning on Postfix SMTPUTF8 support for the first time, we don't want + * to suddenly break pre-existing mail flows that contain UTF8 because 1) a + * client does not request SMTPUTF8 support, and because 2) a down-stream + * MTA does not announce SMTPUTF8 support. + * + * While 1) is easy enough to avoid (keep accepting UTF8 in address localparts + * just like Postfix has always done), 2) presents a thornier problem. The + * root cause of that problem is the need for SMTPUTF8 autodetection. + * + * What is SMTPUTF8 autodetection? Postfix cannot rely solely on the sender's + * declaration that a message requires SMTPUTF8 support, because UTF8 may be + * introduced during local processing (for example, the client hostname in + * Postfix's Received: header, adding @$myorigin or .$mydomain to an + * incomplete address, address rewriting, alias expansion, automatic BCC + * recipients, local forwarding, and changes made by header checks or Milter + * applications). + * + * In summary, after local processing has happened, Postfix may decide that a + * message requires SMTPUTF8 support, even when that message initially did + * not require SMTPUTF8 support. This could make the message undeliverable + * to destinations that do not support SMTPUTF8. In an environment with + * pre-existing mail flows that contain UTF8, we want to avoid disrupting + * those mail flows when rolling out SMTPUTF8 support. + * + * For the vast majority of sites, the simplest solution is to autodetect + * SMTPUTF8 support only for Postfix sendmail command-line submissions, at + * least as long as SMTPUTF8 support has not yet achieved wold domination. + * + * However, sites that add UTF8 content via local processing (see above) should + * autodetect SMTPUTF8 support for all email. + * + * smtputf8_autodetect() uses the setting of the smtputf8_autodetect_classes + * parameter, and the mail source classes defined in mail_params.h. + */ +extern int smtputf8_autodetect(int); + + /* + * The flag SMTPUTF8_FLAG_REQUESTED is raised on request by the sender, or + * when a queue file contains at least one UTF8 envelope recipient. One this + * flag is raised it is preserved when mail is forwarded or bounced. + * + * The flag SMTPUTF8_FLAG_HEADER is raised when a queue file contains at least + * one UTF8 message header. + * + * The flag SMTPUTF8_FLAG_SENDER is raised when a queue file contains an UTF8 + * envelope sender. + * + * The three flags SMTPUTF8_FLAG_REQUESTED/HEADER/SENDER are stored in the + * queue file, are sent with delivery requests to Postfix delivery agents, + * and are sent with "flush" requests to the bounce daemon to ensure that + * the resulting notification message will have a content-transfer-encoding + * of 8bit. + * + * In the future, mailing lists will have a mix of UTF8 and non-UTF8 + * subscribers. With the following flag, Postfix can avoid requiring + * SMTPUTF8 delivery when it isn't really needed. + * + * The flag SMTPUTF8_FLAG_RECIPIENT is raised when a delivery request (NOT: + * message) contains at least one UTF8 envelope recipient. The flag is NOT + * stored in the queue file. The flag sent in requests to the bounce daemon + * ONLY when bouncing a single recipient. The flag is used ONLY in requests + * to Postfix delivery agents, to give Postfix flexibility when delivering + * messages to non-SMTPUTF8 servers. + * + * If a delivery request has none of the flags SMTPUTF8_FLAG_RECIPIENT, + * SMTPUTF8_FLAG_SENDER, or SMTPUTF8_FLAG_HEADER, then the message can + * safely be delivered to a non-SMTPUTF8 server (DSN original recipients + * will be encoded appropriately per RFC 6533). + * + * To allow even more SMTPUTF8 mail to be sent to non-SMTPUTF8 servers, + * implement RFC 2047 header encoding in the Postfix SMTP client, and update + * the SMTP client protocol engine. + */ +#define SMTPUTF8_FLAG_NONE (0) +#define SMTPUTF8_FLAG_REQUESTED (1<<0) /* queue file/delivery/bounce request */ +#define SMTPUTF8_FLAG_HEADER (1<<1) /* queue file/delivery/bounce request */ +#define SMTPUTF8_FLAG_SENDER (1<<2) /* queue file/delivery/bounce request */ +#define SMTPUTF8_FLAG_RECIPIENT (1<<3) /* delivery request only */ + +/* LICENSE +/* .ad +/* .fi +/* The Secure Mailer license must be distributed with this software. +/* AUTHOR(S) +/* Wietse Venema +/* IBM T.J. Watson Research +/* P.O. Box 704 +/* Yorktown Heights, NY 10598, USA +/*--*/ + +#endif |