I have the same problem.

Hi,

I have the problem with odoo 8.0rc1 updated at SA 9.8.14. It must be a bug.

Compose a new message button just does not exists.

It is not a bug, it has been merged with official branches as a commit IPsylone mentioned in his post, but as this question has been already asked on this forum several times, no official statement was given about that.

Hi,

To send a single message to a single user you can - given your mailservers are configured correctly - send a message by viewing the user in form view (e.g. Sales - Customers) and then click on "Send a message" below the user form (I think that's enable through the social media module, not sure though). Just type your email in the text box that opens up. The msg will get sent to the customers email, but with a subject "Re: <email-address>"... so not very handy.

If you use the two little squares just up to the right of the textbox, it pops out the "full email composer" which would allow you to add a subject line. Unfortunately it still seems very buggy, doesn't let you add any additional recipients, and doesn't copy the selected customer in. Hence I've not been able to make a single email go out through that channel, so until you have confirmed it works on your install I would not trust this 100%. (If you type in a subject and message btw, you can hit send and it looks like it's going out without an error, but it doesn't. Don't have access to the server logs on my machine, but I assume that is because there is actually no recipient at all in the recipient field...)

Just in case you are wondering, replies to your message (from the simple text box) do get correctly posted back as a blog entry to that customer, but you don't receive a notification in your message inbox either. To get replies posted I had to make sure that the email address catchall@<yourdomain> is redirected to the inbox you have configured in your mailservers.

Hope this helps.
Frank