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On 05/14/12 12:38, Vinícius Ferrão wrote: |
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> Hello, |
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> |
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> I'm running a postfix mail filtering gateway in a hardened gentoo box |
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> and I really don't know what to do with double-bounced messages. |
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> |
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> Since we have a lot of spam bots attacking our infrastructure, the |
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> double bounce messages cannot be ignored and mail mail queue is growing |
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> with undeliverable double bounce messages. |
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> |
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> Any thoughts on what should be done to handle this? |
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> |
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If you are accepting mail for addresses that don't belong to you, stop! |
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That makes you a backscatter source, and will eventually (rightly) get |
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you blacklisted. |
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You said it's a mail filtering gateway... Usually the reason people |
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backscatter on a gateway is because "it's hard" to get a list of all |
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valid recipients; usually those recipients are on some other mail |
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server. There are ways to do it, though, and you must, e.g. |
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a) Run a cron job that pulls valid accounts every hour. |
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b) Store the email accounts in a database, and allow the gateway to |
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query the database to determine which users are valid. |
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c) Use recipient verification[1]. When receiving mail, your gateway |
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can open a connection to the real mail server in the background, |
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and see if the recipient is valid. |
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We use a combination of all three. We use (a) for an old Windows box, |
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(b) for users stored in Dovecot, and (c) for customers with their own |
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Exchange servers. |
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If you ask over on postfix-users and provide the output of `postconf |
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-n`, there are plenty of people who are able to give you tips relevant |
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to your specific configuration. |
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[1] http://www.postfix.org/ADDRESS_VERIFICATION_README.html#recipient |
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