When you send out your mailing using SendBlaster you have two alternative options: use Direct Send or an external SMTP server. If you use Direct Send, SendBlaster uses its built-in SMTP server, which runs locally. When a mail has to be delivered, the following happens:
- It queries DNS servers in order to find out the recipient's mail server address based on its domain; this is called an MX query and occurs on port 53
- Then it connects to the recipient's mail server and delivers the message through port 25
Two operations occur: each one occurs on a given specific port, which cannot be changed since they are part of a protocol (all MX queries must go on port 53, all deliveries on port 25). If you use an external SMTP server, only one operation is involved:
- SendBlaster connects to the SMTP server and relays the message; any port can be used, as long as the SMTP server can listen on that port. The SMTP server itself will then deliver the message.
As you can easily see, while Direct Send has the big advantage of not requiring any third party service, it has some major drawbacks:
- It involves more operations and therefore takes more time for each message to be sent
- It involves communication with multiple servers, with varying response times (some may be very "far"), thus taking more time
- It is forced to use two exact ports: if the Internet provider is blocking one of them, no direct delivery is possible
There is an even more important thing to consider. Nowadays many mail servers, and a significant number of free services such as Hotmail, Yahoo, etc, refuse to accept messages from any local SMTP server: this is because in the past most spam was sent through local servers; therefore, as a spam-prevention measure, they accept messages only from "public" SMTP servers – servers whose addresses have been registered as public SMTP relays (technically it's a little more complex than that, but this approximation gives you a rough idea). In other words, if you are using a local service (or Direct Send) to send out to Hotmail, the best you can expect is that your message goes straight into "spam" folder – if it gets accepted at all. And if your provider is blocking either port 25 or 53, such as i.e. AOL does, no Direct Send is possible at all. Please note that these drawbacks are common to any local SMTP server – including Windows' built-in ones (some Windows editions, such as XP Professional, come with a built-in SMTP server) and third party ones. Installing any local SMTP server (no matter how much it costs…) on your PC will not help at all. For these reasons, the best choice is using an external SMTP server (and it's the only option if you're with AOL or another provider which blocks port 25). You can use it either alone or in a mixed configuration with Direct Send (SendBlaster is one of the few software which allows this: you can either use the two options as your primary method, and the other as a "backup" in case of error). All providers in fact offer a free SMTP service with their Internet connection; that's because personal e-mail clients (Outlook Express, Outlook, Thunderbird, Eudora, etc) always need one in order to send out mails (they have no direct delivery features). The problem is that your sending speed will depend entirely on the SMTP server's speed. The average SMTP service, which usually comes bundled with your Internet connection, is targeted at small e-mail traffic, and may reveal its limits when you try to use it for serious e-mail marketing:
- Speed may be limited
- The server may not accept more than a given number of messages per hour / per day and refuse extra messages
- No multiple connections may be allowed
- Too strict anti-spam automatic filters may be enforced, leading to legitimate messages being refused
This is ok if you're not doing very large mailings, and you are not under pressure for high performance. But if e-mail marketing is an essential part of your everyday activity, and you find out that your SMTP server performance is poor, you should consider a dedicated service: you'll get faster sending and greater delivery rates (and the cost is probably lower than any other marketing tool after all). The best strategy The best strategy depends on your priorities:
- If you only do occasional or small mailings, or large mailings but without being too concerned about performance, use a mixed configuration: SMTP as your primary method and Direct Send as a backup (in case of error) – or the opposite, see what works best in your case. This way you are sure that most messages are delivered even if you exceed your SMTP server limits.
- If you do frequent or large mailings, or e-mail marketing is very important for your business (and you need both speed and a very high delivery rate: no messages get filtered out as spam), extensively test your Internet provider's SMTP server and, if performance is poor (slow speed or lots of messages don't get delivered or filtered as spam), consider a dedicated third party SMTP service. It's the best technical choice and, used with a desktop mailer such as SendBlaster, it's still much cheaper than any online mailing service.