Terms and concepts
The following terms and concepts are used in this information:
- Backpressure
- CSSMTP stops processing the JES spool file when mail cannot be sent to the target because the connection to a target server is down or unresponsive. CSSMTP resumes processing the JES spool file when a target server connection becomes active.
- Bad spool file
- A bad spool file is a JES spool file that cannot be processed as the result of security, configuration, syntax, readability, or delivery issues. The action taken by CSSMTP is subject to the setting of the BadSpoolDisp statement. For more information about the BadSpoolDisp statement, see z/OS Communications Server: IP Configuration Reference.
- Checkpointing
- If checkpointing is enabled using the CHKPOINT DD statement in the CSSMTP started procedure and there are partially processed spool files on the spool when restarting, CSSMTP attempts to send only the mail from these spool files that was not previously sent, which reduces the duplicate mail that is received by recipients. If CSSMTP is started cold using the -f option, any existing checkpoint records are flushed before CSSMTP is restarted. For information about using the CHKPOINT DD statement in the CSSMTP started procedure and about starting CSSMTP with the -f start option, see z/OS Communications Server: IP Configuration Reference.
- Dead letter
- A dead letter is created and stored for the following reasons:
- An undeliverable mail notification cannot be returned to the originator
- The original mail message was undeliverable, but did not specify an originator
- An error report cannot be delivered to the mail administrators
To ensure that dead letters are stored, configure Store on the DeadLetterAction parameter of the Undeliverable statement. For information about the Undeliverable statement, see z/OS Communications Server: IP Configuration Reference.
For examples of customizing the configuration to handle undeliverable mail, see Customizing the CSSMTP configuration file to handle undeliverable mail.
- ESMTP
- Extended Simple Mail Transfer Protocol
- Extended retry
- If a mail message is not sent to all recipients because the target servers replied with a retry reply code, another attempt to send the message is made after the delay that is defined by the RetryLimit statement. If the long retry limits that are defined by the RetryLimit statement are exceeded, the mail is placed in the extended retry state. The mail is saved in a z/OS® UNIX file system directory for extended retry as defined by the ExtendedRetry statement. If the extended retry limit is exceeded, the mail is marked as undeliverable. For more information about mail retry, see Customizing the CSSMTP configuration file to try mail again. For information about using the RetryLimit statement and the ExtendedRetry statement to configure the retry limits, see z/OS Communications Server: IP Configuration Reference.
- Long retry
- See the definition for extended retry.
- Mail administrator
- The mail administrator is a special user ID for mailing systems, to which CSSMTP delivers error reports for problems detected while processing a spool file from the JES spool data set. For information about using the MailAdministrator statement to configure up to four mail administrator addresses, see z/OS Communications Server: IP Configuration Reference.
- Message content
- The headers and the structured body of a mail message. A separate Multipurpose Internet Mail Extensions (MIME) specification provides the definitions for structured bodies.
- MTA
- Message transfer agent
- SMTP
- Simple Mail Transfer Protocol
- SMTP command
- A command sent from the client to the SMTP server that lets the server know what information is being sent. For example, MAIL FROM: is a command.
- SMTP reply
- The acknowledgement, positive or negative, sent from an SMTP server. Replies are in the ASCII character set of the target server.
- SMTP server
- A network application implementing the SMTP protocol that accepts mail messages from SMTP clients.
- Target server
- A target server is the resolved or configured IP address from a TargetServer statement. The first four target servers are used by CSSMTP. For information about using the TargetServer statement to configure a target server, see z/OS Communications Server: IP Configuration Reference.
- Undeliverable mail
- Mail messages that cannot be delivered. CSSMTP processes and tries
to send all mail messages in the spool file. Sometimes, one or more
of these mail messages might be undeliverable. Examples of what causes
undeliverable mail include:
- A problem with the mail message itself, such as the message size
- A problem with the recipient record (RCPT TO:), such as an unknown mailbox
- A mail message requires a secure connection and none of the target servers support the STARTTLS SMTP command
- Security problems
- A networking problem, such as being unable to reach a target host that has the capabilities that are needed for the mail message
For examples of customizing the configuration to handle undeliverable mail, see Customizing the CSSMTP configuration file to handle undeliverable mail.
- Undeliverable mail notification
- CSSMTP creates an undeliverable mail notification when the ReturntoMailFrom
parameter is set to YES on the Undeliverable statement and the mail
message cannot be delivered. This notification contains the reply
from the target server, describing the reason that the mail message
was undeliverable and the text of the original mail message. If the
undeliverable mail notification cannot be sent immediately, it is
not tried again and is subject to the setting of the DeadLetterAction
parameter of the Undeliverable statement.
For examples of customizing the configuration to handle undeliverable mail, see Customizing the CSSMTP configuration file to handle undeliverable mail.