Best Practices Suggestions for Duplicate Message Problem

Getting duplicate copies of messages can happen. For example, if a user sends an email to both addresseeA, and groupA that contains addresseeA, and DEFER_GROUP_PROCESSING=1 and this attribute is No, then the message immediately duplicates, such that addresseeA gets two copies, one that came directly, and one that took the deferred expansion hop through the reprocess channel for groupA to get expanded.

While disabling deferred group expansion would eliminate the duplicate, that’s not a good idea if you have a lot of large groups. Using expandlimit 1 can potentially cause unnecessary overhead on general, non-group, multi-recipient messages.

To minimize the effect of this situation, the following two solutions are best practices:

• For installations with only a few small groups, setting the default DEFER_GROUP_PROCESSING=1, and this attribute to No, gives you duplicates but also gives you two major benefits:

  • You don’t have to bother running the reprocess channel, which makes a bit less overhead and a bit faster delivery.

  • The potential for eliminating duplicate addresses is increased.

  If your installation has many small groups and only a few large groups, then set DEFER_GROUP_PROCESSING=0, and this attribute to Yes for the few large groups.