With this in mind, be aware that any new recipients created on your mailbox server on the internal network won't be able to receive e-mail messages from external senders before the EdgeSync service has taken place hereafter. A failure in this test indicates that there is a problem routing mail externally.Īs mentioned earlier in this chapter, the EdgeSync service will replicate recipient data from Active Directory to ADAM every fourth hour.

And finally, test sending a message from a local user to a user in a different domain. This test allows you to pinpoint whether or not the problem is a domain-specific issue. The next test is to send a message from a local (within the same domain) user to another user within the domain. This will tell you whether or not the local SMTP server is at least handling basic message transfers correctly. First, send a message from a local (within the same server) user to another local server user. When manually testing SMTP, there are a few different tests that you may want to run to help diagnose where a particular problem lies. Regardless of the messaging, the response code of “ 250” should be consistent. Other servers may respond with a more descriptive message such as “ 250 2.1.0 Sender OK”. In the example shown in Figure 2.13, you see that the server returned a message of “ 250 OK” when sent the “ MAIL FROM” command. In addition to differences in command syntax, different servers respond in different ways to each command. If your SMTP relay is only for internal forwarding, you should also limit where your SMTP relay server can send e-mails.

You should limit who can send e-mails through your SMTP relay server. If you are using the service, you should make sure the service is secure. If you are not using SMTP relay, you should make sure that your e-mail servers have the service turned off. This could greatly hinder your company’s capability to send legitimate e-mails. Eventually, your server may end up on an e-mail blacklist. If your SMTP relay service is open, your system may be spamming without your knowledge. Spammers use open STMP relay servers to forward e-mails through. Open SMTP relay servers are those that are not secure they allow anyone to send a message through them. The problem occurs when there are what’s called “open” SMTP relay servers. This way your internal e-mail servers are not exposed directly to the Internet. An SMTP relay server can be used to forward messages that are destined for or originating from the Internet. SMTP relays can help you protect your internal e-mail servers. SMTP relays are basically servers that are used to forward SMTP messages.

Derrick Rountree, in Security for Microsoft Windows System Administrators, 2011 SMTP Relay

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