wrong subscription logic when routing message into a mail.group

[Csaba TOTH]

Lets say you have a domain: example.com, and a general e-mail address for questions: <email address hidden>. Lets say you have an outer e-mail account for testing: <email address hidden>.

1. Create a POP server, an account in it, and route the <email address hidden> e-mails into that account.
2. Install OpenERP, set up mail alias to "example.com", and fetching that e-mail account. I setted up to create a new record in: "Email Thread", and no server actions.
3. Create a group, and give this <email address hidden> e-mail address to it. I choosed to be a Private group, with no automatic subscription, and allowed to everyone to write into this group.
4. Create a customer (or contact) with this <email address hidden> e-mail address.
5. Write an email from <email address hidden> into the <email address hidden>.

What i wait is this: Every members of this group will get the email, and nothing changes in the members list.
What i get is: that contact (with the <email address hidden> e-mail address) is becomed a follower for that group. And because of this, that contact will get every e-mail afterwards!

This bug is affected by saas3/saas4 version, fix is included (for saas4).