MTAs( Mail transfer agents)

linux_the_greatest · 08-14-2008, 07:33 AM

Hi,
I would like to run two MTAs on one machine. Is it possible.
If yes,then how do i go about? Thanks

garyalex · 08-14-2008, 07:35 AM

Anything's possible

Why would you want to though?

You wouldn't be able to share the same IP and port though...

linux_the_greatest · 08-14-2008, 08:06 AM

I am currently using postfix as my MTA and i would like to put some restrictions in place for some particular users. Postfix can't do that.So that is why i want to run two MTAs on one server.
About the ports i can always change the port numbers and have two network cards i.e two IP address for one Server.

garyalex · 08-14-2008, 08:37 AM

What restrictions do you want to put in for the users by the way?

Mr. C. · 08-14-2008, 08:45 PM

Quote:

Originally Posted by linux_the_greatest

Hi,
I would like to run two MTAs on one machine. Is it possible

Not two MTAs on the same port! And you can't have a single MX record pointing two both of the MTAs anyway. So the question doesn't really make sense.

Quote:

Originally Posted by linux_the_greatest

i would like to put some restrictions in place for some particular users. Postfix can't do that.

Of course it can. What restrictions?

linux_the_greatest · 08-15-2008, 12:53 AM

My MTA is postfix and currently i have 120 users.I want to restrict 100 user from sending mail above 1MB. If i do put the restriction then everyone if affected which isn't my intention. That is why i asked if i can run two MTAs on the same machine,have two network card with different IP addresses and Both MTAs have different Port numbers. Yes all point to the same MX record.

Mr. C. · 08-15-2008, 01:56 AM

Use a policy daemon such as policyd.

billymayday · 08-15-2008, 02:16 AM

Not opining on the benefits of the various approaches, but it's pretty easy to run multiple instances of postfix on one machine. You simply copy the relevant part of /etc/postfix to, say, /etc/postfix1, and create a new startup/shutdown to start postfix with "postfix -c /etc/postfix1 start", etc.. I did this some time ago, more as a exercise for some reason I don't recall, but it definitely works.

See man postfix.

Mr. C. · 08-15-2008, 02:29 AM

...and a separate set of queues (separate instances must have different queues).

You can use restriction classes to do certain things, but message_size_limit is global. What do you do with multi-recipient messages, where one user has a limit and one doesn't? You can't reject the message until the entire message has been received ( to know the size ). Once you've received the message (you've accepted it),you can't reject it for some, but not others.

See: http://groups.google.com/group/list....2a7716f8a444a2

billymayday · 08-15-2008, 03:06 AM

Not sure if that was directed at me, but you get the whole kit and kaboodle duplicated, so it's equivalent to running on a different server.

Note that the OP is wanting to restrict sent message sizes, not received by the look of things btw

linux_the_greatest · 08-15-2008, 06:24 AM

Thanks guys.let me try policyd then revert.

garyalex · 08-15-2008, 09:28 AM

You can try MailScanner which integrates with postfix. It can check message sizes and send friendly rejection messages when the limit is reached. It also has antispam and antivirus features.

Mr. C. · 08-15-2008, 12:26 PM

Quote:

Originally Posted by billymayday

Not sure if that was directed at me, but you get the whole kit and kaboodle duplicated, so it's equivalent to running on a different server.

It isn't clear to everyone that a separate set of queues is required. I just added to your description to clarify for others. The ellipses were added to suggest that the addition is what you would have said.

Quote:

Originally Posted by billymayday

Note that the OP is wanting to restrict sent message sizes, not received by the look of things btw

The message_size_limit parameter is a cleanup(8)/smtpd(8) parameter, and as such controls the size limit of all messages entering into postfix. Hence, it is inbound and outbound.

Code:

main.cf
  message_size_limit = 50000

Eg: via sendmail:

Code:

Aug 15 10:14:42 mrc postfix/postdrop[5918]: warning: uid=0: File too large
Aug 15 10:14:42 mrc postfix/sendmail[5917]: fatal: root(0): message file too big

Eg: via SMTP:

Code:

Aug 15 10:21:51 mrc postfix/smtpd[6429]: connect from localhost[127.0.0.1]
Aug 15 10:21:51 mrc postfix/smtpd[6429]: 5FB51C8246: client=localhost[127.0.0.1]
Aug 15 10:21:51 mrc postfix/cleanup[6434]: 5FB51C8246: message-id=<1218820910.6264.0.camel@mrc>
Aug 15 10:21:51 mrc postfix/smtpd[6429]: warning: 5FB51C8246: queue file size limit exceeded
Aug 15 10:21:51 mrc postfix/smtpd[6429]: disconnect from localhost[127.0.0.1]

billymayday · 08-15-2008, 03:24 PM

Quote:

Originally Posted by Mr. C.

It isn't clear to everyone that a separate set of queues is required. I just added to your description to clarify for others. The ellipses were added to suggest that the addition is what you would have said.

That's fine - I hadn't taken any offence btw

Quote:

Originally Posted by Mr. C.

The message_size_limit parameter is a cleanup(8)/smtpd(8) parameter, and as such controls the size limit of all messages entering into postfix. Hence, it is inbound and outbound.

I was really only responding to the reject point - the presence of multiple recipients doesn't matter if the restriction is intended for outgoing messages since if it's over the limit it gets rejected period, but it could get messy on inbound

It'll be interesting to see how the pilicyd goes. Hopefully it will get posted.

popowich · 08-15-2008, 04:14 PM

Are you set in your ways on using postfix? I prefer qmail for smtp relays. You can accomplish what you would like to do with 1 install of qmail and 2 smtpd configurations with each of the two smtpd's running on a different port. You can set the DATABYTES variable in each instance for the size of the e-mail that you would like to allow. A question that I don't believe has been addressed yet is how are you going to police who is connecting to each instance? Is this an environment where the different users talk to each other and one can tell the other about the "big" setting, or it this for clients who are not likely to figure out how to abuse your system and there is some flavor of auth mechanism involved?

-Raymond