When you try to send or receive messages on a computer that is running Microsoft Exchange Server 2003, Microsoft Exchange 2000 Server, or MIcrosoft Windows Small Business Server 2003, you experience one of the following symptoms:
- Exchange server does not accept Simple Mail Transfer Protocol (SMTP) messages from certain Internet domains.
- Exchange server cannot deliver SMTP messages to certain Internet domains.
The sender may receive the following non-delivery report (NDR) that contains the 5.5.0 error code. This code indicates a generic SMTP failure.
> Your message did not reach some or all of the intended recipients.
> Sent:5/24/01 6:41 PM
> The following recipient(s) could not be reached:
> firstname.lastname@example.org on 5/24/01 6:41 PM
> Your mail system could not find a way to successfully communicate with the destination system. Please notify your administrator. <Server.source.com> #5.5.0
Additionally, the Windows Event viewer on the Exchange server that is sending the message may contain an event 4000 or an event 4001 that is similar to the following:
- The IP address does not match the domain name that is used in the return address of the e-mail message.
- A pointer (PTR) record does not exist or is not valid for the source SMTP server's IP address.
Note If your Network adapter that is connected to the Internet is using a dynamic IP address, you may have to configure Exchange Server to route mail from the source.com domain through an SMTP connector to a smart host.
Note You can configure the Exchange server to reject incoming connections by specifying a domain name on the SMTP virtual server. When this is done, reverse lookups are performed on all connection attempts. This setting is available under Connection Control on the Access tab when you right-click the SMTP virtual server and then click Properties.
- Make sure that your public DNS records that are hosted on your DNS server are correct. On your DNS server, examine the following:
- You must have an MX record for your domain that points to a valid Host (A) record. For example, the MX record for source.com points to mail.source.com. mail.source.com is a valid e-mail server.
- Make sure that the Host (A) record points to a valid IP Address. For example, make sure that mail.source.com points to 22.214.171.124. This is the correct public IP Address for your e-mail server.
- For every SMTP server or Exchange Server computer that sends outgoing Internet e-mail, make sure that there is a valid PTR record for the Public IP address of that sending SMTP server or Exchange Server computer. This may be a firewall, a router, or another device that used to publish your domain information to an IP address that is visible by Internet hosts.
For example, your Exchange Server computer is behind a firewall with an internal IP of 10.10.10.1, and the firewall has an external IP of 126.96.36.199.
When the Exchange Server computer sends e-mail to source.comdomain through the firewall, the receiving mail server sees that the 188.8.131.52 IP address is connecting for SMTP Communication. The receiving e-mail server performs a reverse DNS lookup against this IP address, not necessarily the MX record. The e-mail server must find a PTR for 184.108.40.206 pointing to a valid host record in the source.com domain.
The mail servers of some Internet domains require that you create a valid PTR record that points the sending server's IP address to the local SMTP domain namespace. Sometimes these mail servers require that the PTR record match the actual FQDN of their SMTP Virtual Server on Exchange. Typically, this is the MX record. These Internet domains include AOL.com, Qwest.net, Mindspring, Earthlink, and Outlook.com. To send mail to these domains, create a valid PTR or a reverse lookup record on your company’s external or Internet DNS server.
If you telnet to the destination server's SMTP port and then attempt an SMTP conversation, the conversation will look similar to the following:
C:\telnet server.destination.com 25
220 mail.destination.com ESMTP Postfix
554 <email@example.com>: Sender address rejected: Domain not found
220-rly-ya06.mx.aol.com ESMTP mail_relay_in-ya6.3; Fri, 20 Jan 2006 22:15:42 -05 00
220-America Online (AOL) and its affiliated companies do not
220- authorize the use of its proprietary computers and computer
220- networks to accept, transmit, or distribute unsolicited bulk
220- e-mail sent from the internet. Effective immediately: AOL
220- may no longer accept connections from IP addresses which
220 have no reverse-DNS (PTR record) assigned.
For more information about configuring an SMTP connector in Exchange 2000 and Exchange Server 2003, click the following article number to view the article in the Microsoft Knowledge Base: