Direct Delivery

This is a method of email communications, in which an email program is able to deliver messages directly to a recipient’s email server without having to relay through an intermediate mail server. This results in fewer bounce-back email messages and fewer points of failure. Another advantage of direct delivery is that this process reduces the danger of ISPs revoking accounts for sending excessive mail; that makes this ideal for some mass-email senders.

However, this process does have disadvantages. It can sometimes be slower than other methods of delivery. Some domains require a PTR record, or a reverse-DNS for the sender’s IP address, meaning that more information must be traded between the back end of  both servers. Also, the process can be slower because of the time spent during two separate DNS queries when the sender’s program will seek out their recipient’s mail server and their mail server’s IP address. Finally, some domains will refuse messages from those on Policy Block Lists, meaning that messages may be immediately blocked rather than allowing the user the option to view or refuse the message.

From a technical standpoint, the process is fairly simple. For direct delivery, the domain name is extracted from the user’s email address. (The domain name is the information that is listed after the @ symbol.) A DNS query finds the mail server, which is often simply mail.domainname.com. Then, it finds that mail server’s IP address, which may look like: 11.22.33.44. Finally, the sender’s email program connects to the IP address on Port 25 to deliver the email message.