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My mail server bounces mail, but PN's relays let it through

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My mail server bounces mail, but PN's relays let it through

Due to the amount of carp e-mail I've started receiving, on my SMTP gateway I turned on the option to verify the e-mail senders identity. Bingo - most of the rubbish stopped... for a day.
I run a daily cron job to finger the PN e-mail backup servers incase my ADSL line dropped so I get all e-mail I missed, but what I've found is when my e-mail server originally rejects an incoming message, the sender's SMTP gateway is falling back to the PN backup mail server which accepts it, then when my system finger's PN's backup mail server it accepts all of the junk e-mail as well.

I'm guessing this is because the 'sender' mail server is correctly identifying itself, being the PN relay.

Is there anything I can do about this?

SteveC
2 REPLIES
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My mail server bounces mail, but PN's relays let it through

There is nothing you can do about this, as it is is the way Spammers operate.

Rather than give up on the primary gateway as they should, they fallback until there are not more MX servers to connect to. Only then do they give up.

This is mainly due to the very problem that backup servers in most deses are setup to accept this junk for later collection.

To reject the e-mail at SMTP level, you need to be without the other MX records.
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My mail server bounces mail, but PN's relays let it through

Thanks for the quick reply acarr.

From your reply it would appear that setting up sender verification and RBL's on my smtp gateway are close to useless then.
I'm assuming this will be the same if I implement my own RBL lookup?

If so, then I guess if I really want to tackle spam I have 2 options:
1) Ask PlusNet to remove all backup MX records from my domain
2) Implement some type of content filtering only (as this would be the only type to catch e-mails no matter where they come from).

Or do you have any other suggestions?

SteveC