We have members who are not part of the "predefined" list of mail servers that require "via " address modification.?
I think the "list" is discovered rather than defined. That is, Groups.io
checks the sending service's DMARC records to determine if the
modification is necessary (policy = reject).
?
Is there a way to either force it for all members (similar to Yahoo) or at least for those who are having issues?
No, I don't think so. You could ask for that feature in beta, but I don't think there's a point to it.
?
I see 2 places where this is necessary: the user's server has an SPF record associated with it which does not include ...
It would be very unusual if it did. And wrong, given that Groups.io's servers are not in any way under the control of the member's email service. ?
... or the user's server does not allow internal email addresses originated externally.?
If their rule were that simple their users couldn't participate in mailing lists at all - at least not lists that have fellow users. That is, if both Alice and Bob use 's service, they'd not be able to see each other's posts.
The only services that should be having that kind of issue are those that have elected to use a "reject" policy in their DMARC records. Those services are incompatible with traditional mailing lists, but Groups.io (and Y!Groups and some others) have adapted to that. Most other lists I'm on simply don't support users of those services as members.
In both cases, it is extremely important to be able to "turn on" the "via " functionality.
No, only in the case of a reject policy in their
DMARC
record, I think, and that's handled. ?