A friend of mine and I have two mailinglists (one on google groups, one on yahoogroups) concerning a similar topic.

It would be convenient to connect those mailing lists, so that every message is sent to both lists. However, we want to avoid "loops" (a message that is sent to every list more than once).

As both lists have a high "identification potential" simply copying all users to the other list is not an option.

  • Could you clarify what identification potential is please.
    – Toby
    Commented Nov 4, 2011 at 14:26
  • of course: both mailing lists have really cool names - the users wouldn't want to switch to the other one. But the main fact is: we wouldn't merge the mailing lists to one, it's simply not an option. We'd rather want to implement a solution that simply forwards the incoming mail to the other list.
    – Marcel
    Commented Nov 4, 2011 at 15:05
  • How many users would you have between you? Commented Feb 2, 2012 at 21:26

2 Answers 2


The solution may depend on both lists settings. You should always simulate with test lists, before implementing on the real list.

Using one forward email account subscribed to both lists, customized settings and email filters may solve the problem. Gmail accounts have some basic filters, but gmail (and other free providers) will not forward if you send to many emails on a specific day. Gmail (and other free providers) may not let you customise the "Reply-to" field and that may become a problem with some settings.

In case simpler solutions don't work, you may have to script filters for your own forward mail client/server. This scripts should analyse mail headers and craft a forward message modifying them.


What you can try is merging the two lists (not manually) but using an online utility like the following.


Copy the two lists in each box. This will give you the unique list excluding any duplicate entries. Try this out!

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