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sendmail and discarding incoming FROM address's

http://www.faqs.org/docs/securing/chap22sec178.html
im referring to this online info where i want to block incoming FROM: address's
i currently block incoming TO: address's already

like ....

jack@aol.com DISCARD
john@tootles.com DISCARD


but how does sendmail know whether its a from or to address ?
i just today wanted to add the from address from an address.

currently the access table discards all to address's above so it must be working

Question is how does it know if i add a new address to refer to it as a FROM address ?
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aot2002
Asked:
aot2002
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1 Solution
 
wesly_chenCommented:
Hi,

> how does sendmail know whether its a from or to address
All the emails have "From: xxx@xxx.xxx" and "TO: yyy@yyy.yyy" fields, that's how sendmail to distingush where the email from
and whare it should send to.

   However, according to http://www.faqs.org/docs/securing/chap22sec178.html,
/etc/mail/access is for "From" not for "TO".

   So whatever email addresses you "DISCARD" in /etc/mail/access", your users will not receive "from" those email addresses.
It's sort of spam control.

Regards,

Wesly
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aot2002Author Commented:
>>>>/etc/mail/access is for "From" not for "TO".

ok but why would it be currently blocking to address's ?
hmm doesnt make any sense ?

can i block from address's or no ?




> how does sendmail know whether its a from or to address
>>All the emails have "From: xxx@xxx.xxx" and "TO: yyy@yyy.yyy" fields, that's how sendmail to distingush where the email >>from and whare it should send to.

No no i mean how does sendmail know it in the access.db file not the email ...

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wesly_chenCommented:
> can i block from address's or no
Yes.

> how does sendmail know it in the access.db file not the email
access.db is for "from". So sendmail check every email's "FROM:" and match with access.db
Please see the following URL:
http://www.sendmail.org/~ca/email/doc8.12/cf/m4/features.html
----
The access db gives you the ability to allow or refuse to accept mail FROM specified domains for administrative reasons. Moreover, it can control the behavior of sendmail in various situations.
-----

> but why would it be currently blocking to address's ?
I'm not sure.
You can put your yahoo or hotmail address in access and send an email to your company address to test.

Wesly
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