External MTA Settings

[SynUK]

If I set both the "Web mail MTA Hostname" and "Relay MTA for external delivery" to an external ISP's SMTP server smtp.isp.co.uk, and I send an email to another user on my Zimbra server, does this mean that all email goes :

[mailbox] -- [external SMTP] -- [mailbox]

or does it go :

[mailbox] -- [zimbra MTA] -- [external SMTP] -- [zimbra MTA] -- [mailbox]

I'm trying to avoind a user in the web mail interface having to wait for my ISP's mail server to accept the mail. Ideally I would like it to use option 2 above.

Thanks for any help.

[uxbod]

It will be delivered internally as the domain is local to the server