SMTP error - Outgoing Mail Problem
 

Dear All:

Since my mail server's rDNS information wasn't my domain name, I have changed the rDNS (PTR Record) information correctly of the live mail server (postfix + dovecot).

Now suddenly, users have been unable to send mails through the relay where IMAP is working as OK.

Many DNSBL servers had listed my ip (x.x.x.x) as spam source, and after requesting now it's unlisted, but still our users can not send mail to outside world.

In mail queue there was too many mails and continuously /var/log/maillog file is being filled with new logs. After "postsuper -d ALL" mail queue is cleared but the mail log is continuously filling the file.

In the mail log file, there was many SMTP errors (450, 421 etc.) like "450 4.7.1 Recipient address rejected" or "421 4.7.0 ts01 messages from x.x.x.x temporarily deferred due to user complaints"

But now there is only the below errors:


Please help me to clarify the situation and as well as find the solution.

Thanks...

Congratulations, you just deleted all your users queued mail!

The logs show lots of properly rejected spam relay attempts and a reject of mail to an unknown user.

Where is the logs of the problem?

^^^This.
It seems you might have previously been running an open relay.
This would explain your listing on blocklists, and the large amounts of attempts to relay via your server.
Unfortunately, errors like that do not just go away when you fix the problem, but will haunt you for some time yet.

Yes, you are right. Previously it was set up as open relay.

My current Infrastructure is as drawn below:

.......................................................................
| LAN | -----> | Mail Server | --(?)---> | ISP Cloud |
.......................................................................

As I suspect, my business opponent and some bad IT guys are working against me. Now I am thinking to implement a firewall type appliance (?) so that I can save the mail server for inside and outside holy world from the attackers. What can be a good suggestion if I wish to choose any Open source/free/low cost system. [I have spare CPUs, so I can easily install any ISO and keep it running to serve as the firewall]

First of all tonmoy, never reveal the email address in any forum ,blog. If you want to show the logs like this replace the real email id.

OK For open source and low cost system, I will suggest you to use iredmail. Its community version is also available which is free. For how to setup you can read my this post and explore it.

Second thing it is a open relay ,you are inviting hackers and spammers. I will suggest you to install postfix 2.10,use spamassasin,amavisd,clamav, SMTP authentication, required HELO request ,configure DNSBL in main.cf file. There are much more to configure and manage mail server . Search a good how to and test your mail server with telnet command.

He didn't. The real addresses are munged, the rest are spam.It is no longer an open relay, as shown by the rejects listed above.
Get a clue and offer some real advice ... and take your advertising elsewhere.

refuse to talk to me: 501 5.5.4 Invalid domain name on postfix
 

Hi there,
when i send email on my postfix. i am getting a return mail with bellow error code

"refuse to talk to me: 501 5.5.4 Invalid domain name"

* i have four domain in this server
* my ip all ways blacklisted in CBL

Have you know any solution for this

Yes.
Stop sending spam and use a proper domain name.

edit: ... and stop hijacking other peoples threads.:tisk:

sorry bro...

Thanks everyone for trying to help me...

How did it go?
Are you still having trouble with being blacklisted?

Would SPF also be advisable for prevention of unintended relay on the mail server? I'm not an expert on this subject; what do others feel?