Help installing Postfix on CentOS - Null Client

Additionally, I'd like the scripts to be able to send as if the emails where coming from any address.

So that if I have a contact form, and that form is filled in - then the person enquiring effectively becomes the "from" address and when I and others receive the email we can simply hit reply.

You can install postfix with:

yum install postfix

Then you need to take make a few minor config changes in /etc/postfix/main.cf

Change the following parameters:

myhostname - set to your server's hostname

mydomain - set to your domain name

I think you can get away with just that for outbound only. If you block incoming traffic to port 25 you don't need to worry about open relay issues (and postfix is pretty secure out of the box anyway).

Then start it up with: service postfix start

That should be all you need… if you want to wrap scripts around the mail command and it's not there try running yum install mailx (can't remember if it will be there already off the top of my head).

Hope this helps

You can configure Postfix as a null client.

If you need to authenticate with the mail relay, enable client SASL. On Ubuntu 8.04, Postfix is already linked with the Cyrus libraries; don't know about CentOS.

000 - Thank you - I did what you said and all seems to be working fine.

Vance - As I'd already followed 000's instructions and it seems to be working as intended - is there anything that I should look at from the links you provided?

Finally, having just followed 000's instructions (only edited the 2 entries) is there anything else I need to/can disable to optimise the memory/cpu usage of postfix?

Thank you both again - linode and it's community is amazing.

Regards,

Chris

I had a quick look at the link Vance posted to the Postfix manual - looks ok (some are optimizations, e.g. listening on loopback only…read the notes below it to see if you feel any line of the config would be better for your needs).

Optimization wise you shouldn't need to do anything, Postfix is very lightweight in this kind of setup.

As 000 notes, it's probably worthwhile to set "inet_interfaces = loopback-only" in /etc/postfix/main.cf. This is a bit more robust than using a firewall to block outside connections. My other references were for a slightly different type of setup than you seem to be using.

Also note that many programs will send error reports to root. If you don't plan to read mail locally on your Linode, you'll probably want to edit /etc/aliases to direct mail for root to your real e-mail address. Don't forget to run newaliases after making your edits.

You'll want to be careful about letting people send arbitrary messages via a web page where they get to pick the "To:" address - this can easily cause you to become a spam source.

Hi 000 & Vance,

I've made the loopback change and suggested - is there anyway to check if the alias modification and newaliases worked or do I need to wait till something tries?

Thank you both again for you advice.

Regards,

Chris

You should be able to test whether mail to root works by running the following command on your Linode.

$ /usr/sbin/sendmail -t
To: root
Subject: Test

testing 123
.

If it works, you'll get a message at the address you set the alias to with the subject "Test" and the body "testing 123". You can also look in your mail logs to see that the message was delivered (or delivery was attempted).

Hi Vance,

Well the scripts are working correctly, however the aliasing isnt. :(

Here is what I have:

Maillog:

The last entries are:

Jan 11 18:46:04 li140-172 postfix/pickup[31811]: 5302D3B231: uid=0 from= <root>Jan 11 18:46:04 li140-172 postfix/cleanup[31824]: 5302D3B231: message-id=<20100111184604.5302D3B231@babygirl>
Jan 11 18:46:04 li140-172 postfix/qmgr[31812]: 5302D3B231: from=<root@babygirl.twenty4.org>, size=299, nrcpt=1 (queue active)
Jan 11 18:46:04 li140-172 postfix/smtp[31826]: 5302D3B231: to=<root@babygirl.twenty4.org>, orig_to=<root>, relay=none, delay=20, delays=20/0.01/0/0, dsn=5.4.4, status=bounced (Host or domain name not found. Name service error for name=babygirl.twenty4.org type=A: Host not found)
Jan 11 18:46:04 li140-172 postfix/cleanup[31824]: 5A4D33B232: message-id=<20100111184604.5A4D33B232@babygirl>
Jan 11 18:46:04 li140-172 postfix/bounce[31827]: 5302D3B231: sender non-delivery notification: 5A4D33B232
Jan 11 18:46:04 li140-172 postfix/qmgr[31812]: 5A4D33B232: from=<>, size=2176, nrcpt=1 (queue active)
Jan 11 18:46:04 li140-172 postfix/qmgr[31812]: 5302D3B231: removed
Jan 11 18:46:04 li140-172 postfix/smtp[31826]: 5A4D33B232: to=<root@babygirl.twenty4.org>, relay=none, delay=0, delays=0/0/0/0, dsn=5.4.4, status=bounced (Host or domain name not found. Name service error for name=babygirl.twenty4.org type=A: Host not found)
Jan 11 18:46:04 li140-172 postfix/qmgr[31812]: 5A4D33B232: removed</root@babygirl.twenty4.org></root></root@babygirl.twenty4.org></root@babygirl.twenty4.org></root> 

Looking at the above - I notice that it says there is no A record for babygirl.twenty4.org - which is correct, I haven't setup an A record for "babygirl" - do I need to?

aliases

I left everything else the same and modified the last time to read:

root:        me@myemailaddress.com

main.cf

I changed the entries you said to say:

myhostname = babygirl
mydomain = twenty4.org

I entered babygirl for myhostname (as thats what I have in in my /etc/hostname - which I did after following this tutorial).

And twenty4.org is one of the sites I'm running on my linode.

I ran newaliases after making the change and have also reloaded postfix.

Have I done anything incorrectly?

Any advice is appreciated.

Thanks,

Chris

@Chris Owens:

myhostname = babygirl

I think that should the full domain name, not the local name.

What's the output of "postconf"? On my machine it shows the fully qualified domain name (FQDN) for "myhostname".

sweh - that worked - just did a quick test and recieved the test email to "root".

I set $myhostname to: server.twenty4.org

One last question - the to/from address of the email I received appears as - "root@server.twenty4.org" - is there a way of changing this to something more friendly (e.g. linode@twenty4.org)?

Many thanks again to all for your help.

Regards,

Chris

Do you plan on doing a lot of emailing from the command line?

@Xan:

Do you plan on doing a lot of emailing from the command line? I see what you mean…

I just checked mailing through a PHP script and it honours the from address and doesn't use "root@server.twenty4.org".

Thanks for your help and apologies for my ignorance on this last issue.

Best regards,

Chris