topic Sendmail sent mails limit / thresholds in Operating System - Linux

Sendmail sent mails limit / thresholds

Ruben C. — Mon, 13 Nov 2006 08:05:37 GMT

Hi,

One of the servers I admin is a sendmail server. It has > 8000 accounts, and our users are majorly dumb users using dumb passwords.

Last Friday night, I've found out that one of the accounts (user 'simon' with pass 'simon') was used to send thousand of emails to randomly generated hotmail accounts. Due to it, we've been banned and now our connections to any of hotmail's MX time out. I've solved temporarily the problem using another IP for outgoing mails, but I know that's not the solution.

Of course the solution is setting strict and complex passwords, but this task can be done easiy due to politic issues in the company with the users, and will take some time (weeks, months) to be able to be done.

So I'd like to know if there's any way of limiting the amount of emails sent using an authed sesion per unit of time. For example... 100 mails per hour? Something in that way. I'm not talking about limiting the number of opened sessions as, in fact, the spammer opened "only" 200-300 sessions but in each session sent 10,20,30,40,50,60,etc emails. Limiting the number of rcpt's isnt a solution for this problem due to this.

Any suggestion for this?

Thanks in advance.

Re: Sendmail sent mails limit / thresholds

Alpha977 — Mon, 13 Nov 2006 08:34:04 GMT

So, i think is better to change a password with something like : SimoN or SimoN123

But if don't want, try to check the parameter :
confCONNECTION_RATE_THROTTLE into the sendmail.mc

This limit the max connection

Re: Sendmail sent mails limit / thresholds

Ivan Ferreira — Mon, 13 Nov 2006 08:38:50 GMT

Hi Ruben, Welcome to the forum (Bienvenido!!).

Probably this is what you are looking for:

http://www.milter.info/sendmail/milter-limit/

But you should re-check/enforce your access policy (firewall policy and relay policy) until you implement the password restrictions.

Por favor, asegurate de ver tambien:

http://forums1.itrc.hp.com/service/forums/helptips.do?#28

Re: Sendmail sent mails limit / thresholds

Alpha977 — Mon, 13 Nov 2006 08:38:56 GMT

Check also:

default_process_limit
initial_destination_concurrency
local_destination_concurrency_limit
default_destination_concurrency_limit

and

smtpd_error_sleep_time
smtpd_soft_error_limit
smtpd_hard_error_limit

This last 3 parameters are for the errors (if it generate address, more are wrong...)