SMTP responses

SMTP commands arrive over a TCP connection (to your terminal) or over a batch SMTP connection. With either connection, a response to each command is generated. All responses are prefixed with a 3-digit number. You can determine the response by inspecting the first digit of the response code:

First digit	Description
2	Indicates a positive response. Command accepted.
3	Indicates a positive response. Send the data associated with the command.
4	Indicates a temporary negative response. Try again later.
5	Indicates a permanent negative response. The command has been rejected.

If SMTP commands arrive over a TCP connection, all responses (positive or negative) are returned over that TCP connection. If SMTP commands arrive over a batch SMTP connection, all responses are written to the batch SMTP response data set.

If verbose mode is enabled for a batch SMTP connection, SMTP returns the batch SMTP response data set to the origination point of the spool data set. The origination point is determined from the NETDATA header if the data set arrives in NETDATA format, or the MAIL FROM command if the data set arrives in punch format. If the batch SMTP connection is not in verbose mode, the batch SMTP response data set is not returned to the point of origin, and is discarded.

If an error occurs during the processing of commands over a batch SMTP connection, such as reception of a negative response (with a first digit of 4 or 5), an error report is mailed back to the sender. The sender is determined from the last MAIL FROM command received that was valid. If the sender cannot be determined from a MAIL FROM command, the sender is assumed to be the origination point of the batch SMTP command data set. The error report mailed to the sender includes the batch SMTP response data set and the text of the undeliverable mail.

All SMTP commands and data that arrive over TCP or batch SMTP connections are subject to the restrictions imposed by constants that are defined in the SMTPGLOB object. A reference copy of this object is included in the SEZACMAC library; the object lists constant value declarations that are used by SMTP.

The default values of some of these constants are:

Command lines must not exceed the MaxCommandLine value (512 characters).
Data lines must not exceed 998 characters in length for mail RFCs (this value does not include the carriage return/linefeed character (CRLF), which must be added to each data line). Internally, SMTP uses a slightly larger MaxDataLine value to hold record attributes.
Note: If an incoming note has data lines between 251 and 1024 characters long, these notes are not processed by the TSO RECEIVE command like conventional notes. The recipient user is prompted to enter a new data set name for the RECEIVE command to temporarily store the note text. When the prompt has been responded to, the text is presented to the user along with any other notes that are to be processed.
Path addresses must not exceed the MaxPathLength value (256 characters).
Domain names must not exceed the MaxDomainName value (256 characters).
User names, the local part of a mailbox specification, must not exceed the MaxUserName value (256 characters).

The limit on the number of RCPT commands in a single SMTP job is 2000. If you have more than 2000 RCPT commands, the excessive RCPT commands receive a failure reply code 552 Too many recipients. Abend B37 can still occur for either of the following reasons:

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