I'm running Mailman version 2.1.29.
I have a Mailman email list that has around 500 subscribers, who are all
members of an organization who have opted-in to the list.
One of the email addresses on the list used a custom personalized domain,
which started bouncing. I didn't notice the bounces at the time.
Eventually, Google started sending the list moderators messages saying "Our
system has detected an excessively high number of invalid recipients
originating from your account," and Gmail started rejecting list messages
that were being sent to the list subscribers who use a Gmail address. I
removed the bouncing email address from the list, and soon after that Gmail
started accepting messages from the email list again.
This seems like a very precarious situation to be in... I have a list of
500 email addresses, and Google starts rejecting all incoming email from my
list just because 1 of 500 email addresses was bouncing.
I sought help from someone at my hosting provider who seems to be
knowledgeable about Mailman configuration. He said that the problem was
that Mailman was batching up the emails and sending a single email to the
entire batch, putting each individual email address in the "RCPT TO" field.
So when a bounce happened, Gmail was able to associate the bad address from
my domain with the bounce that was happening on the bouncing personalized
domain. The advice for fixing the problem was to set the "personalize"
setting to "Full Personalization", which would prevent Google from making
that association. I think this worked (but don't know for sure, since I
don't know that we've had any bounces since then).
The problem with "Full Personalization" is that the email headers are
being rewritten, which is confusing to users. Now, if someone sends an
email to the list, the message that is delivered to each recipient has the
recipient's email address in the "To" header and the list email address in
the "Cc" header. It works, but it's confusing (and some people's email
filters now have to be changed).
1) Given my description of the initial problem, is "Full Personalization"
the best way to fix the issue?
2) Is there a way to fix the issue that doesn't involve rewriting the
headers so that the email list address is in the "Cc" field?
3) Would upgrading to Mailman 3 help fix this issue in a better way?