[support] Unable to send e-mail. Contact the site administrator if the problem persists

[Jamie Holly]

On 12/15/2013 3:50 PM, Tim Johnson wrote:
>    Hello Jamie :
> > What's your email address set in the E-Mail address field on
> > Administration > Configuration > System > Site information?
>    tim at tj49.com
>
>    The errors listed above are the ones when I attempt to send
>    mail using the PHP mail() function in the test PHP file.
>    FYI: on Mac OSX _www is the apache user.

You still need to check that _www is a user in Postfix. Since you have 
your Postfix configured to verify_sender, it's asking the server if that 
is an actual user or not. If it isn't then the email is rejected. It 
really all depends on how your installation of Postfix is setup for the 
user base (aliases, ldap, etc.)
>    It is a different issue when I attempt to send email using the
>    smtp authentication module - see below
> > ini('sendmail_path', '/usr/sbin/sendmail -t -i -f tim at akwebsoft.com');
>    That was added, and caches were cleared.
>
>    Did a test send from my smtp auth module.
>    I got three error messages (as per subject line) from the module.
>    Looking at the drupal logs - I see this:
>
That INI setting won't have any affect on SMTP. SMTP sends emails 
through the PHPMailer package, which doesn't use mail() at all, but 
rather uses PHP's sockets and handles everything internally. Try 
disabling SMTP and using that ini setting, see if you can send through 
Drupal. That will use the regular PHP mail() function, which is nothing 
more than a wrapper for the system's sendmail command.

Jamie Holly
http://hollyit.net