Recipientlimit, recipientcutoff, deferralrejectlimit, disconnectrecipientlimit, disconnectrejectlimit, disconnectbadcommandlimit, disconnectbadburllimit, disconnectcommandlimit Channel Options

Maximum allowed recipients or bad commands
The,   and (new in MS 6.2)   channel options, when placed on a source channel, impose per-channel limits on the number of recipients for a submitted message. Each of these options accepts a single integer argument; they default to no limit. (Note that setting  or    to   has no effect; only  positive limit values will be enforced.)  These options are all per-channel (as opposed to per-SMTP-server) analogues of the  ,  , and   SMTP channel settings.

limits the total number of recipient addresses that will be accepted for the message; additional recipients will be rejected. The text in the rejection is configurable via the   MTA option, which by default is "too many recipients specified". The error is a temporary rejection by default, but if bit 4 (value 16) of the   MTA option is set, then the rejection is permanent. So in the case of attempted SMTP message submissions, the default temporary error, with the default error text, would appear as: 451 4.5.3 too many recipients specified whereas with the default  text but with bit 4 (value 16) of the   MTA option set, then a permanent error would appear as: 550 4.5.3 too many recipients specified compares the total number of recipients that were presented to the MTA to the specified value and a message will not be accepted for delivery to any recipients if the value is exceeded. In the case of attempted SMTP submissions, the message will be rejected at the DATA command with the SMTP rejection: 451 4.4.5 Error ending envelope - Too many recipients specified for this message New in MS 6.2, and supported only for SMTP (not for LMTP),  limits the number of bad (failing) addresses that will be allowed during a single session; after this number, all subsequent recipient addresses, good or bad, will be rejected with a temporary error. In the case of attempted SMTP submissions, additional RCPT TO: commands will be rejected with the error: 451 4.5.3 Too many rejections; try again later while attempted VRFY: commands will be rejected with the error: 451 4.5.3 Verification blocked; too many rejections Similar limits controlled on a per-user and per-domain basis can be configured via LDAP attributes; see the MTA options,   ,    and.

The  channel options are new in Messaging Server 6.2 (except:   new in Messaging Server 7.1,   new in Messaging Server 7.4-18.01). They are supported only for SMTP, not for LMTP. Each takes an integer argument specifying the maximum number of (recipients, rejections, bad commands, or commands, as applicable) which will be accepted for messages submitted via that source channel; any more will result in the MTA forcing a disconnect of the SMTP session, after issuing an error response to the client consisting of (for ): 421 4.7.0 Session recipient limit reached; disconnecting for  in MS 6.2: 450 4.7.0 Session bad recipient limit reached; disconnecting or in MS 6.3 and later (MS 6.3 also being when behavior was enhanced so that rejected MAIL FROM&#x27;s count against the, whereas in MS 6.2 only rejections at the RCPT TO or VRFY stages counted; MS 6.3 is also when behavior was enhanced so that   is checked at the VRFY stage and with a negative value applied at the VRFY stage, whereas previously such VRFY rejections were counted but the disconnect would not be triggered until a subsequent RCPT TO attempt "noticed" that the threshold was exceeded): 421 4.7.0 Session rejection limit reached; disconnecting or (for ): 450 4.7.0 Maximum number of commands exceeded In the case of the  or   channel options, once the limit is exceeded, the error-response-and-disconnect normally will occur after the next MAIL FROM or RSET command (or in the case of   in MS 6.3 and later, potentially after a failed VRFY attempt). (Note that because the disconnect usualy does not happen until after a subsequent MAIL FROM or RSET, these  channel options would most often be used in conjunction with other channel keywords or  TCP/IP-channel-specific option  settings: perhaps   or   to limit the number of recipient addresses accepted, or   or the    TCP/IP-channel-specific option setting.)  In the case of ,  , and  , once the limit is exceeded the error response is issued and the MTA forces the disconnect.

The  channel option is new in   Messaging Server 7.4-18.01. A single integer parameter is accepted specifying the number of invalid  BURL commands  that will be allowed before disconnecting. The default is 3.

Note that VRFY attempts are counted separately from RCPT TO attempts against the recipient count; that is, one may have up to the recipient limit of VRFYs and up to the recipient limit of RCPT TOs. The VRFYs are counted, but counted separately from RCPT TOs. In contrast, failed VRFY attempts are added to the same rejection counter used for counting failed RCPT TO attempts and MAIL FROM attempts for purposes of comparison against the rejection limit; that is, one may have up to the rejection limit of any combination of failed VRFYs, MAIL FROMs, or RCPT TOs.

When the  has been reached (or a TCP/IP-channel-specific option setting of     has been reached), a client VRFY attempt will receive from the MTA an error response: 451 4.5.2 Verification blocked; too many rejections Note that prior to MS 6.3, the error was instead: 452 4.5.2 Verification blocked; too many bad addresses. Note that the   mapping table&#x27;s    flag may also be used to set limits such as   or.

For forcing IMAP or POP disconnection after a specified number of protocol errors -- similar to the  effect for SMTP -- see the   IMAP or POP option.

See also:
 * ALLOW_RECIPIENTS_PER_TRANSACTION
 * REJECT_RECIPIENTS_PER_TRANSACTION
 * ALLOW_REJECTIONS_BEFORE_DEFERRAL
 * error_text_recipient_over MTA Option
 * use_permanent_error MTA Option
 * use_temporary_error MTA Option
 * ldap_recipientlimit MTA Option
 * ldap_recipientcutoff MTA Option
 * ldap_domain_attr_recipientlimit MTA Option
 * ldap_domain_attr_recipientcutoff MTA Option
 * BURL_ACCESS mapping table
 * Addresses channel options
 * SMTP and LMTP protocol channel options
 * Long address lists or headers channel options
 * Channel options
 * TCPIP-channel-specific options
 * FROM_ACCESS mapping table
 * maxprotocolerrors Option