Blocking mail

[David Crowe]

I am running Sendmail with the access_db configured as a relay. I want to drop email going to a specific address located further in the mail system. I know that I can use the access component to drop mail coming from specific addresses but I don't see anyway to drop mail going to an address. Does any one have any ideas?

[Steven E. Protter]

You can add specific ip addresses or email addresses to your acess text database and build a new access_db.

example:


Sabra2564i86@yahoo.com 550 Spam reject. We charge $500/spam message.

After running the script gen_cf on the HP box this address anything coming from it will generate and automated reply requesting a storage fee of $500.

Pretty mean.

SEP

[David Crowe]

That would work if I was trying to block email FROM a domain. What I am trying to do is block email going TO a specific address i.e. admin@yourdomain.com located inside your relay.

[Geoff Wild]

Easy, in /etc/mail/acces

admin@yourdomain.com reject

Then makemap your access db and restart sendmail.

Rgds...Geoff

[David Crowe]

I tried that using the DISCARD option and it didn't work. It seems to work only on originating addresses not destination addresses. Does the REJECT option work different than the DISCARD?

[Geoff Wild]

Yes - reject is different then discard.

You could also block your entire domain and then explicitly grant only certain id's:

yourdomain.com reject
you@yourdomian.com allow
someoneelse@yourdomain.com allow


Rgds...Geoff

[W.C. Epperson]

The logic that checks "From:" address is in the check_relay ruleset. There's no corresponding check in check_rcpt for the "To:" address. You'd have to write a rule and add it--good luck. Sendmail.cf rules make me dizzy after looking at one for more than a few minutes.

What I generally do in this instance is to go to the local delivery SMTP server for the address and forward its mail to an undeliverable address like "returntosender@mydomain.com". How to do this depends on what kind of MTA it is. With sendmail, it's /etc/mail/aliases. With Groupwise, you can do it with the admin interface.

[W.C. Epperson]

Geoff,

It's "OK", not "allow", with the default sendmail rulesets, isn't it?

[Steven E. Protter]

If you want to stop mail from going to a whole domain, you could set up a dns record for that domain on your internal DNS server. Point it at a local linux box and all the mail will go there instead of externally.

Just a wild alternative. The access file should be manipulated to do the job though.

SEP

[W.C. Epperson]

Oh, and as SEP advises, use a 500 series smtp error code, e.g. "user@domain.com 571 Not around here, you don't". 500 series is permanent error/rejection. If not used, the delivering relay may regard the error as transient and keep banging on the door (if it's not RFC-compliant, it may do so anyway).