On Wed, Oct 29 2014, David Belohrad wrote:
> - 'standard' behaviour is, that the email sent becomes read-only so with
>   'q' keystroke I can bury the buffer with the email. However when I
>   have implemented this, I have noticed that when I 'confirm' the
>   template, I go back into the buffer 'sent mail to...', but this the
>   *THE BUFFER IS NOT READ ONLY* and 'q' will just generate a character,
>   and then I have to kill this buffer using C-x k with additional 'yes'
>   because the buffer was modified. Quite annoying and I don't know how
>   to resolve this

I'm unsure about this. The change below may fix it accidentally.

> - second thing is, that I'd like to avoid at all opening the capture
>   template and just dump it into the file without any modifications
>   ongoing. The only 'modification' which comes into my mind is a setup
>   of an additional tag describing the email being attached to some
>   project...

Change the template to...

    ("@" "Email outgoing sync. USED INTERNALLY" entry (file+datetree (concat my-org-files "emails_sent.org"))
    "* EMAIL %c :EMAIL:\n%?\nEntered on %T\n" :immediate-finish t)
(i.e. add ":immediate-finish t")

...and you will never see the capture buffer for this entry.