Loopcheck= Normal

Loopcheck= Full

Loopcheck= None[,Allow-Bounces]

Loopcheck= option1[,option2][,optionn]

This keyword is not available in LISTSERV Lite.

Determines the type of loop checking performed by LISTSERV to avoid perpetuating mail loops. The default is "Loopcheck= Normal". Loop checking is configured on a list by list basis only.


Misuse of this keyword can and will allow mailing loops onto your list!

The various Loopcheck= parameters are defined as follows.  "Normal", "Full" and "None" must be specified alone (except in the special "None,Allow-Bounces" case, and except for "Spam-Delay(n)"), whereas the other options may be specified together as required.



LISTSERV uses its "normal" suite of loop checking heuristics.  Tests considered to be obsolete are not conducted. This is the default for Loopcheck= beginning with LISTSERV 14.5.  See the LISTSERV 14.5 release notes for more details.


LISTSERV uses its full suite of loop checking heuristics to check incoming mail for loops.  This includes tests considered to be obsolete.


All LISTSERV loop checking and "command to list" checking is disabled for this list. WARNING: "None" tells LISTSERV that, by definition, anything that reaches its reader is NOT a delivery error. It is never a good idea to use this parameter except in special cases where a bug is suspected in the loop checking heuristics. Generally this parameter should not be used without checking with L-Soft first, and only for the diagnosis of an existing problem.


Allows the list to accept error messages that would normally be bounced to the list owner.  This makes it possible to direct the Errors-To= keyword setting to a LISTSERV list rather than to a specific person. "Allow-Bounces" MUST be specified in conjunction with "None". Specifying just "Loopcheck= Allow-Bounces" will result in a syntax error when the list header is stored.


Allows the list owner to disable the check for "known mailer origins" such as MAILER, POSTMASTER, ROOT, UUCP, et al. Mail whose 'From:' field is the address of the local mailer is still trapped, but wildcard checks on the mail origin are disabled.


Allows the list owner to disable the check for identical text in the body of incoming mail only. LISTSERV relies only on the Subject: field of the mail message to determine whether or not mail is looping. This is a very dangerous option: it means that any mailer not using one of the "standard" subjects known to LISTSERV will cause a loop.


Allows the list owner to disable CRC (cyclical redundancy check) check of incoming mail. CRC loop checking calculates a "checksum" based on the contents of the mail message and compares it to other incoming mail to spot duplicates.


Allows the list owner to disable the anti-spamming filters to incoming mail.


Allows the list owner to modify the number of minutes LISTSERV holds mail from non-subscribers before releasing it to the list. The assumption is that, within n minutes, a spam alert may or may not arrive regarding non-subscriber mail. The list owner can disable this function for his list by coding "Loopcheck= Spam-Delay(0)", or can tune it to his preference by simply specifying the number of minutes for LISTSERV to hold the mail. The default is 10 minutes, or "Spam-Delay(10)".

Please note carefully that L-Soft does not recommend changing Loopcheck= from the default value unless you are prepared to accept the very likely possibility of a mail loop occurring on your list; a situation for which L-Soft would not and could not be held responsible for. The only exception would be the "Loopcheck= NoSpam" (which might be necessary to keep administrative mail to multiple lists on a single host from triggering the anti-spamming filter) or "Loopcheck= Spam-Delay(n)" options, neither of which stops canonical mail loops per se.

See also Filter= and Safe=.