There’s a bug with Google Groups and Gmail that’s describe pretty well here, along with a solution.
From my understanding, Google Groups’ default setting is this: set the “Reply-To:” field to the group email address no matter who sent the email. Where this causes problems is if the original sender is not part of the Google Group.
In Gmail, when you hit “Reply-All”, it will reply to everyone in the “To” field, as well as the “cc” and “Reply-To” field, but it won’t automatically include a reply to the original sender if that person isn’t in the cc list. This should be expected, but isn’t exactly intuitive unless you’re looking at the email headers. What the original sender really should be doing is including themselves in the cc list if they wish to be further included on the discussion, but most people (like me) will forget.
A way to work around this, is to set up the Google Group to not set a “Reply-To” field at all (as described in the link above), so that its up to the email client to decide what to do. For Gmail, this seems to be do not set the “Reply-To” field to anything. This makes it so when someone hits Reply-All, the email is sent to the original sender, and the Google Group, along with everyone else that may have been on the email, to the cc list.
The downside of this setting is that if a user forgets to hit reply-all, the email will just be sent directly back to the sender, and not the Google Group, because no Reply-To field has been set.
That’s all kinda confusing, so there’s a nice table that may help:
| Google Group Setting | Reply-To email field | Gmail’s “reply” | Gmail’s reply all |
| Replies sent to whole group | <group address> | <group address> | Does not include sender’s original email address |
| Users decide where replies are sent | <unset> | <sender’s address> | Includes all addresses |
