SMTP Gateways

Table of Contents

This option allows you to specify one or more backup SMTP servers. If PostCast Server is unable to deliver a message, it can forward it to a backup SMTP server. If only certain domains are unable to receive messages from PostCast Server, you can use this option to forward those messages to your ISP's SMTP server.

If you are using PostCast Server on a laptop or you regularly connect to the Internet through different ISPs, make sure that you specify a working ISP's SMTP server for each Internet connection. If one of the SMTP servers fails because you are not connected to the correct ISP, the program will try to deliver a message through the next backup SMTP server on the list.

How the message is sent

The program arranges the list of gateway servers by using their assigned priority. Disabled SMTP gateways will not be used for sending. The priority can be any of these values:

1. Highest
2. High
3. Normal
4. BelowNormal
5. Low

The program first tries to send a message to a server with the highest priority. If the sending process fails, other servers will be used. The program continues sending the message until all servers are used or the message is successfully delivered.

It is important to notice that if the message is successfully sent to one of the gateways, that does not automatically guaranties that it is delivered to the recipient. If the gateway server has problems delivering the message, in most situation the message will be returned to the sender. This is somehow different than the way PostCast Server is delivering messages where you immediately know whether the message is successfully sent or not.

What happens if a message cannot be delivered using this method?

The program will simply follow the default logic. If, for example, the domain list is specified, the program will move the message to the Bad folder. If the "Use for undelivered messages" option is selected, the program will move the message to the Bounced folder and try to return it to the sender if "Return undeliverable message to the sender" option is selected in the Settings/Administration window.

Do not use SMTP gateways

Disables the SMTP Gateways feature completely. The program will deliver all messages by directly connecting to each recipient's mail server.

Use gateways for undelivered messages

The program tries to send a message until the condition in the Settings/Administration window is met. If a message could not be delivered after certain number of days/retries/hours, the program will try to send it using specified gateways.

If you are using a dial-up connection to the Internet, make sure that the "Do not send messages if a Dial-Up connection cannot be detected" option is selected in the Settings/Dial-Up window, otherwise if the connection is not established, the program will always mark the message as bad.

Use gateways whenever an error occurs

The program will try to deliver the message to the recipient's mail server after any error that occurs during the sending process. Be careful with this option. The program will forward messages that are obviously wrong and the gateway server will also have problems delivering them. For example if you are sending message to e-mail address where the domain clearly does not exist, the program will first get an error from the DNS server and then forward the message to a gateway server. The end result is receiving the message back from the gateway server after it failed to deliver the message to the recipient.

Types of errors

LAN Error. After sending to a LAN address. The program first tries to deliver the message to a server on the Internet. If that attempt fails, the program tries to send the message to the LAN address. If both attempts are unsuccessful, the program will use SMTP gateways.

DNS Error. If a DNS entry for the recipient's e-mail address cannot be retrieved or there are some problems with the DNS server. If the program gets an error from a DNS server or if a DNS server is not available, the message is sent using SMTP gateways.

SMTP Error. If the recipient's server exists but the program detected an error during the sending process. After any error that occurs during the sending process, the program will use SMTP gateways.

Use gateways to send messages only to specified domains

This option allows you to specify a list of domains for which the program will use SMTP gateways instead of direct sending.

If you experience that the program cannot sent messages to only some domains and that all other domains work correctly, you should use this option to ensure that those messages are always delivered.

Blocking of dynamic IP addresses implemented by AOL is a good reason for using this option. Dynamic IP address is assigned to your computer when you establish the Internet connection to your ISP. If AOL's server determines that your message originates from the dynamic IP address, the message will not be delivered. You can use this option to forward the message to your ISP's SMTP server. Their server's (non-dynamic) IP address will be the source of your outgoing messages.

Always use SMTP Gateways

The program will not deliver any message to a recipient's mail server. Instead, all messages will be forwarded to SMTP gateways. The messages will not be sent directly from your computer.

It is recommended to use this option if you want PostCast Server  to only collect messages from e-mail clients and forward them to some other SMTP server or servers.