Motivation: I’m changing my ticketing system so that messages with a friendlier subject line. Instead of ‘Subject: [SNAFU #1] summary’, I’ll change it to use ‘Subject: [HELPDESK #1] summary’.<\/p>\n
Another colleague suggested we use Is procmail right for me? (http:\/\/unixgeeks.org\/security\/newbie\/unix\/procmail\/procmail.html<\/a>)<\/p>\n I think we can do better than a serious Unix hack. I think Postfix can handle this.<\/p>\n How to do it? <\/p>\n First, I created a test environment: two Debian 9 virtual machines:<\/p>\n I’m not going to add DNS entries, though, so I’ll be relying on their IP addresses on my internal network:<\/p>\n I installed As an initial test, I tried to send a message from one machine to the other:<\/p>\n But this resulted in an error from the mailer-daemon:<\/p>\n The solution? Enclose the IP address in square brackets:<\/p>\n (Thanks to Is there a way to send an email to an IP address directly?<\/a>, which I believe is the first time I have ever seen anything useful on the Quora web site.)<\/p>\n The two test systems can send messages to each other. Great!<\/p>\n Now, to change the subject line. A ServerFault post, postfix header_checks to rename email subject<\/a>, looked like exactly what I was looking for (and a similar scenario motivated that question).<\/p>\n Following the answer there, I added the following to And I created Don’t forget to reload Postfix, required by just about any Postfix change:<\/p>\n I sent a test message from I checked the logs at I reproduced this problem using I changed the filename (not strictly necessary, but good for my sanity) and tried This produced no output, no error message, and a return code of 1. Why didn’t it match?<\/p>\n It turned out I needed to modify the regular expression, since (Using I ran a couple successful tests using Now to test an actual e-mail message.<\/p>\n First, I updated Don’t forget:<\/p>\n I tested it from It appeared in root’s inbox on I sent another message with a different subject line just to confirm it was unchanged by the Other useful resources:<\/p>\n I wanted to change the subject line of messages sent from my ticketing (queueing) system from [SNAFU #1] to the friendlier [HELPDESK #1]. Using Postfix header_checks I was able to accomplish this.<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[362],"class_list":["post-2692","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-postfix"],"_links":{"self":[{"href":"https:\/\/osric.com\/chris\/accidental-developer\/wp-json\/wp\/v2\/posts\/2692","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/osric.com\/chris\/accidental-developer\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/osric.com\/chris\/accidental-developer\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/osric.com\/chris\/accidental-developer\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/osric.com\/chris\/accidental-developer\/wp-json\/wp\/v2\/comments?post=2692"}],"version-history":[{"count":9,"href":"https:\/\/osric.com\/chris\/accidental-developer\/wp-json\/wp\/v2\/posts\/2692\/revisions"}],"predecessor-version":[{"id":2704,"href":"https:\/\/osric.com\/chris\/accidental-developer\/wp-json\/wp\/v2\/posts\/2692\/revisions\/2704"}],"wp:attachment":[{"href":"https:\/\/osric.com\/chris\/accidental-developer\/wp-json\/wp\/v2\/media?parent=2692"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/osric.com\/chris\/accidental-developer\/wp-json\/wp\/v2\/categories?post=2692"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/osric.com\/chris\/accidental-developer\/wp-json\/wp\/v2\/tags?post=2692"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}procmail<\/code>. As unixgeeks.org says:<\/p>\n
\nProcmail is a serious unix hack. On the other hand, it does a pretty good job.<\/p><\/blockquote>\n\n
\n
postfix<\/code> and mutt<\/code> on each:<\/p>\n# apt-get install postfix mutt<\/code><\/pre>\n# sendmail root@192.168.0.18 < test.eml<\/code><\/pre>\n<root@192.168.0.18>: bad address syntax<\/code><\/pre>\n# sendmail root@[192.168.0.18] < test.eml<\/code><\/pre>\n\/etc\/postfix\/main.cf<\/code>:<\/p>\nheader_checks = pcre:\/etc\/postfix\/header_checks.pcre<\/code><\/pre>\n\/etc\/postfix\/header_checks.pcre<\/code>, containing the following:<\/p>\n\/^Subject: \\[SNAFU #(\\d+)\\](.*)$\/ REPLACE Subject: [HELPDESK #$1]$2<\/code><\/pre>\n# postfix reload<\/code><\/pre>\nbar<\/code> to foo<\/code>, and an error message arrived in root’s mailbox on foo<\/code>:<\/p>\nSubject: Postfix SMTP server: errors from bar.osric.net[192.168.0.19]<\/code><\/pre>\n\/var\/log\/mail.log<\/code> and found the following:<\/p>\nJul 8 16:47:29 foo postfix\/cleanup[10927]: error: unsupported dictionary type: pcre<\/code><\/pre>\npostmap<\/code>:<\/p>\n# postmap -q 'Subject: [SNAFU #1]' pcre:\/etc\/postfix\/header_checks.pcre\r\npostmap: fatal: unsupported dictionary type: pcre<\/code><\/pre>\nregexp<\/code> instead:<\/p>\n# postmap -q 'Subject: [SNAFU #1]' regexp:\/etc\/postfix\/header_checks.regexp<\/code><\/pre>\n\\d<\/code> is a Perl-ism:<\/p>\n\/^Subject: \\[SNAFU #([0-9]+)\\](.*)$\/ REPLACE Subject: [HELPDESK #$1]$2<\/code><\/pre>\n[[:digit:]]<\/code> instead of [0-9]<\/code> would also work.)<\/p>\npostmap<\/code>:<\/p>\n# postmap -q 'Subject: [SNAFU #1]' regexp:\/etc\/postfix\/header_checks.regexp\r\nREPLACE Subject: [HELPDESK #1]\r\n\r\n~# postmap -q 'Subject: [SNAFU #1] more text' regexp:\/etc\/postfix\/header_checks.regexp\r\nREPLACE Subject: [HELPDESK #1] more text<\/code><\/pre>\n\/etc\/postfix\/main.cf<\/code> to point to the updated filename with the corresponding dictionary type:<\/p>\nheader_checks = regexp:\/etc\/postfix\/header_checks.regexp<\/code><\/pre>\n# postfix reload<\/code><\/pre>\nbar.osric.net<\/code> (192.168.0.19), using the following file, test.eml<\/code>:<\/p>\nSubject: [SNAFU #1] test message\r\n\r\nThis is a test.<\/code><\/pre>\n# sendmail root@[192.168.0.18] < test.eml<\/code><\/pre>\nfoo.osric.net<\/code> (192.168.0.18) with the updated subject as expected:<\/p>\nDate: Sun, 8 Jul 2018 17:03:56 -0500 (CDT)\r\nFrom: root <root@bar.osric.net>\r\nSubject: [HELPDESK #1] test message\r\n\r\nThis is a test.<\/code><\/pre>\nheader_check<\/code>.<\/p>\n\n