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February 15, 2020 23:09
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An Exim System Filter to create a Domain Jail for Emails
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| # Block example.com from sending to any other domain | |
| if first_delivery | |
| and ("$h_from:" contains "@example.com") | |
| and ("$h_to:" matches "@(?!example.com)[a-z0-9_.]+") | |
| or ("$h_cc:" matches "@(?!example.com)[a-z0-9_.]+") | |
| or ("$h_bcc:" matches "@(?!example.com)[a-z0-9_.]+") | |
| then | |
| headers add "X-Org-Subject: $h_subject" | |
| headers remove Subject | |
| headers add "Subject: EmailJail'd: $h_x-org-subject" | |
| headers add "X-EmailJail: This domain is under an Email Jail and cannot send mail to external domains." | |
| seen fail "Your domain is under an Email Jail. This means you cannot send emails to external domains." | |
| endif |
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UPDATE: Fixed in Rev 3.
This has a flaw when sending to multiple to addresses - if a single address has our domain, then it will send to all TO addresses.
Not sure how to fix or improve this...
https://gist.github.com/mallardduck/2daa41ce6c591aa898de10c947c80c1e#file-email_jail-L6