Using a google apps group as sender?

Yes, that’s possible. Follow these instructions: Send mail from a different address or alias

Briefly:

1. Sign in to Gmail on the web
2. Go to Settings > Accounts > Send Mail As
3. Enter the Group email address and verify it

Postman remains configured with the mailbox email address, whereas the From: address, for example in Contact Form 7, should be configured to use the Group email address.

Perhaps in a future version I will allow the user to maintain separate addresses for Sender (the mailbox) and From (the group email).

I’ve added a new From field in the Postman configuration in 1.6.18.

The Envelope Sender has to be a real user (eg. [email protected])
The Message Sender is set to the Group email (eg. [email protected])

Then check both “Prevent plugins from changing the From address” checkboxes.

One thing I’ve found, is Google will not send a Group email message to the original sender if they are also in the group. So in the scenario above, if the recipient is [email protected], [email protected] will not receive the message, though everyone else in the group will.