delay_check, blacklist_recipient how to block all recipients except some
R Curtis
mail to internal servers. In last week, the domain name of this
server has gotten the attension of some spammers that have decided to
send emails in the thousands per day to any...@ourdomainname.com.
This results in bounced messages from the internal server going back
out of the sendmail machine to the forged addresses of these bogus
emails and the bounced replies coming back and crippling the sendmail
machine.
I have searched the groups and read README.cf and as a result tried
adding and using the delay_check, "friend" feature as well as
blacklist_recipient feature to no avail. I found recommendation on
similar post from Claus Assman to add the delay_check feature and then
add to access.db
To:ourdomain.com REJECT
To:vali...@ourdomain.com OK
The problem is that although this makes sendmail machine start
replying to these spammers that the invalid users are disabled and
stops the crush of replies from bad addresses, Then emails to valid
users designated above also get bounced from the sendmail machine with
a No Relay message.
I have tried the above setting in the access file as well as the
To:vali...@ourdomain.com friend
setting in attempt to get valid email through to no avail. It is as
if the OK setting above is ignored. The access file before trying to
use the blacklist_recipient feature has following pertinent settings:
ourdomain.com RELAY
internalserver RELAY
Then in the mailertable, we have
ourdomain.com ESMTP:internalserver
Can anyone help me with this ? We want to stop all emails getting in
at sendmail box to invalid users on the internal server.
If I simply remove the To:ourdomain.com REJECT
our internal email servers get messages again, but unfortunately, also
all the spam bounces.
R Curtis
solved the problem. Had to add a /etc/mail/relay-domains file and
add our domain name to it that is forwarded to internal server. In
redhat 7 installs of sendmail this file was not created evan though
referred to in the /etc/sendmail.cf file. After adding this file and
putting our domain name in it, all works as expected and described by
putting in access file
To:ourdomain.com reject
To:vali...@ourdomain.com OK