hey friends, My Mail Server is configured on FC3 (Postfix+Dovecot+Clamav+Fetchmail).I am facing one problem few of the mails from my domain are getting rejected. For example if any user from my domain is sending the mail to a user on rediffmail.com domain that mail is getting rejected. My Scenario is such we have one catchall with the ISP i download all the mails from the ISP mailbox through fetchmali.For sending the mails the local mail server with postfix running on it.The postfix is configured to authenticate with the ISP mail server before sending the mails. If the authentication is properly configured then why the mails are getting rejected see below ankush1711@xxxxxxxxxxxxxx>: host mail2.rediffmail.com[203.199.83.4] said: 553 Message from xx.xx.xx.xx( Public Ipaddress of my company) rejected - see http://spamblock.outblaze.com/xx.xx.xx.xx (in reply to RCPT TO command) The link http://spamblock.outblaze.com/xx.xx.xx.xx (in reply to RCPT TO command ) shows this: Explanatory Note : Your mail has been rejected because it has been sent direct from a mailserver running on a dialup or other dynamic IP listed in the SORBS DUHL dynamic IP blocklist at www.sorbs.net We block mail from known dialup pools and other dynamic IP blocks, due to the ever present risk of "direct to MX" spam originating from spammers running bulkmailer software equipped with smtp engine capablities, and "remailer" virii such as Swen and Sobig, which have their own smtp engines to remail copies of themselves. Please set your mailserver up so that it sends out mail through your ISP's mailserver, or through any other mailserver with a static IP address that you have access to. http://www.mail-abuse.com/support/an_rteoutgoing.html is an excellent resource which lists the steps required to set up a "smarthost" in several mailservers. This list is maintained by SORBS. If you believe this entry to be in error and you are actually a static IP, please submit a request using this form: https://www.dnsbl.sorbs.net/scgi-bin/dulexclusions Thanks, Outblaze Postmaster (postmaster@xxxxxxxxxxxx) How to stop my mail server to become a part of Spam World. I want to test that my local mail server is getting authenticated with the ISP mail server.Sasl_finger is a tool that I know shows some statistics regarding this but it does not itself checks by sending a mail.Is there any other tool for checking the authentication with the ISP . We have one Public IPaddress ,NAT is configured on the ADSL Router to give all the users in the LAN access to the Internet. In postfix/main.cf the entries for authentication as below: smtp_sasl_auth_enable = yes smtp_sasl_password_maps = hash:/etc/postfix/passwd smtp_sasl_security_options = noanonymous I have not configured TLS/SSL for postfix. The entries for passwd file are as ISP mailserver username:password. Please guide me what wrong I am doing and how to correct it . Thanks & Regards Ankush