ISP mail server help.

ckob · 08-17-2007, 07:43 AM

I work for a small ISP in NY

I have a mail server running RHEL 4 with postfix + squirrelmail over the past few weeks someone has been sending 100K+ emails through my server and im not sure how to stop them. Could anyone recommend how I could tighting my security on the mail server? sorry if this is vague I can provide more details if needed.

ArcLinux · 08-17-2007, 08:52 AM

First of all, is the user a client or a generic user on the net?
Is the user using your smtp server or their own and your just noticing the traffic on 25?

ckob · 08-17-2007, 09:01 AM

generic user I think.

if it helps here is some of my mail log, im in no way a linux guru know enough to get by.

Quote:

ug 17 09:53:00 mail postfix/smtp[21226]: CA46A5600C7: to=<neptune1619@aol.com>, relay=none, delay=67663, status=deferred (connect to mailin-01.mx.aol.com[64.12.137.249]: server refused to talk to me: 554 (RLY:B1) http://postmaster.info.aol.com/errors/554rlyb1.html )
Aug 17 09:53:01 mail postfix/qmgr[4383]: 2171D5637D6: removed
Aug 17 09:53:01 mail postfix/smtp[24412]: connect to mailin-03.mx.aol.com[64.12.138.120]: server refused to talk to me: 554 (RLY:B1) http://postmaster.info.aol.com/errors/554rlyb1.html (port 25)
Aug 17 09:53:01 mail postfix/smtp[18826]: connect to mailin-01.mx.aol.com[64.12.137.184]: server refused to talk to me: 554 (RLY:B1) http://postmaster.info.aol.com/errors/554rlyb1.html (port 25)
Aug 17 09:53:01 mail postfix/smtp[20645]: connect to mailin-02.mx.aol.com[205.188.157.25]: Connection timed out (port 25)
Aug 17 09:53:01 mail postfix/smtp[21907]: connect to mailin-04.mx.aol.com[205.188.159.216]: server refused to talk to me: 554 (RLY:B1) http://postmaster.info.aol.com/errors/554rlyb1.html (port 25)
Aug 17 09:53:01 mail postfix/smtp[17790]: connect to mailin-01.mx.aol.com[64.12.137.184]: server refused to talk to me: 554 (RLY:B1) http://postmaster.info.aol.com/errors/554rlyb1.html (port 25)

I can sit here and watch thousands of those go by and the emails it sends to go in alphabetical order as they are sent.

ArcLinux · 08-17-2007, 09:19 AM

http://www.postfix.org/rate.html
Take a look at that page and search for concurrency.

If that does not work for you, you may have to implement a commercial or personal queue system that you can limit messages sent per IP addr per day.

You can also slow down the response rate of postfix.

all else fails, MAC bind the user and block all email.

ckob · 08-17-2007, 09:51 AM

great thanks ill take a look.

ckob · 08-17-2007, 10:01 AM

do you or does anyone else know of anything out there to limit the amount of emails sent from an ip to a domain per day?

for example if joe@whatever.com sends a email to *@aol.com how can I limit joe to only 5 msg per hour to that domain?