A lot of the large email services have filters in place to prevent not-so-bright mailing list servers creating feedback loops. Google and Yahoo do for certain.

I’d suspect you’re getting caught by that code, especially if your mail server is on a range of IP addresses designated as home or small business services. Contact postmaster@google.com to find out how you can get your server past that.

From: otrs-bounces@otrs.org [mailto:otrs-bounces@otrs.org] On Behalf Of Carlos Ribas
Sent: Tuesday, September 04, 2012 11:11 AM
To: User questions and discussions about OTRS.
Subject: Re: [otrs] Problems with group of email

Gerald, 

    Sorry, english is not my mother language, so I guess I was not clear. 

    Imagine an email of google groups. I'm telling that the customer registered his account with an email from google groups (eg group@company.com) and that group has client1@company.com and client2@company.com. When this client creates a new ticket, a response is not sent to client1@company.com and client2@company.com (clients from group@company.com)

    Message logs says the email was sent:

Sent auto response (SendAutoReply) for Ticket [2012090406] (TicketID=118, ArticleID=216) to 'customer name <customer_group@googlegroups.com>'.

Sent email to 'customer name <customer_group @googlegroups.com>' from 'My OTRS server <my_otrs_server@company.com>'. HistoryType => SendAutoReply, Subject => [Ticket#2012090406] RE: testing;

    But the email was not sent, I also checked spam box. It works well in a "single" email, it's odd.