Troubleshooting network problems

This tutorial will guide you through how troubleshoot the most common configuration errors (on your Pc or local network) that may prevent SendBlaster (as well as any other group mailing software) from sending any message. It is important to understand that this will help only in those situations when you cannot send even a single message: this is a strong indicator that there is a network configuration problem (otherwise at least some messages would be sent). The steps to solve the problem differ depending on which delivery method (Direct Send or Smtp) you are experiencing problems with. Therefore we offer separate instructions. But first we have to issue a very important warning:


Security Warning

In the following tutorial, we suggest disabling your firewall and antivirus as a temporary measure only, in order to quickly troubleshoot your problems or at least find out where they come from. But the most appropriate final strategy is to properly configure your security tools instead of disabling them. This may be a time-consuming operation, but it is really needed to keep your system protected. Knowing how to configure your security tools is essential unless you have an administrator that does the job for you. That said, let's see how to make things work.


Direct Send

For each recipient, an MX query is sent to your DNS server in order to resolve its mail server address (based on the e-mail address domain, the part that follows the "@" sign). Then, SendBlaster connects to the mail server and delivers the message. The query is made through port 53, while the message is delivered through port 25. Any firewall or antivirus that blocks one of these ports will prevent successful delivery.



You should completely disable firewall and antivirus, do a test mailing, then re-enable them and configure them properly (allow use of ports 53 and 25).

  1. Temporarily disable your firewall, or configure it so that it allows SendBlaster to connect to the Internet without any restrictions.
  2. Temporarily disable your antivirus. Disabling mail checking is not enough when you use Direct Send: since direct delivery is used not only by legitimate tools as SendBlaster, but also by some worms for propagating themselves, some antiviruses do not allow direct delivery and block MX queries on port 53. This protection is called "Internet worm protection" or something similar, and it's totally separate from outgoing mail protection. For this reason, it is important that you completely disable your antivirus instead of simply stopping outgoing mail checking. (Some antiviruses cannot be stopped, even manually by user, unless they are uninstalled: if this is your case, we strongly suggest that you switch to a better antivirus.)

If your Pc is connecting to the Internet through a gateway on the local network, you should repeat these steps on the gateway too. If you still cannot send, there may be some problem on DNS autonatic recognition then you may have to manually enter your DNS address:

In SendBlaster "Send" form, manually enter your DNS server IP address (ask your Internet Service Provider if you don't know its address).

If these steps don't help, your Internet Service Provider is likely to be blocking direct delivery (port 53, 25 or both): this is a policy adopted by some large providers such as AOL, and unfortunately there is nothing you can do about it (apart from changing your provider…).).



Messages are relayed to an Smtp server, a dedicated service which will later deliver them to their final destination: the recipients' mail servers. This is usually faster as the Smtp server is (or at least should be) quicker and always available. Port 25 is normally used, but your Smtp server may require using a different port.



You should completely disable your firewall (to be re-enabled and properly configured later) and configure the antivirus so that it does not check outgoing mail.

  1. Temporarily disable your firewall, or configure it so that it allows SendBlaster to connect to the Internet without any restrictions.
  2. In your antivirus program, disable outgoing mail checking (if you're not sure how to do this, completely stop the antivirus to temporarily get-around this problem)

If your Pc connects to the Internet through a gateway on the local network, you should repeat these steps on the gateway too.

Make sure you entered the correct Smtp server address in SendBlaster "Send" form. The Smtp address may need to include a port specification (format is "servername:port"), as some Smtp services run on a "custom" port (while default is 25).

There is no "guessing" here: things will work only if you enter the correct parameters, as your provider gave them to you. If you are unsure about something (server address, port, username and password if needed), ask your provider instead of just guessing (it is very unlikely that it will work). Please note that, unless you subscribed to a dedicated Smtp service, you have to use your Internet Service Provider's Smtp server: using any other Smtp server will not work. If you connect to the Internet through different providers, you may have to change the Smtp configuration in order to match the connection you are currently using. Now, try to send a very small mailing at low speed (use "Slow" profile on SendBlaster): if you did everything properly (firewall and antivirus disabled, both on local PC and on the gateway, and correct settings for the Smtp server), you should be successful. If you receive a "connection refused", "message refused" or similar error (any error which sounds like "the Smtp server is there but doesn't want to talk to you"), that means that the Smtp server address is right, but you are not authorized to use it: either you need authentication or you are using some other ISP's Smtp server. The good news is that the network configuration is probably ok, so you should just check your settings more accurately (ask your ISP if you are unsure about authentication issues). If you are receiving an "incorrect IP or service unavailable" error, it means that you either did not enter the Smtp server name correctly, or there still is some problem on the network. At this point, after an additional check of the server address, you could try to completely disable your antivirus if you haven't done it yet; or you may require further assistance from your network administrator.

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