Internal and External mail in Zimbra?

[Firstime]

Hi everybody here.
First of all I want to apologize for my english and if I write this topic where I can't.
At this moment I have installed ZCS in Ubuntu 8.04 LTS 23 bit.
I want to create this server in the company I'm working.
My idea is that all users in my company have, at least, 2 email accounts configured in his zimbra user.
One account is the internal mail, (my server is emailzimbra.net) so I have my email firstime@emailzimbra.net working. I can read and send emails withouth any problem.
But my problem is when I create my ISP's emails account (my isp is for example is myisp.com), I can read my emails because I configured my settings but my BIG BIG problem is that I can't send emails because I don't know where I have to configure my SMTP server (in this case smtp.myisp.com), so when I send some mail from firstime@myisp.com to user@myisp.com I recibe in firstime@emailzimbra.net INBOX the Error Mail.

Someone can help me for configure SMTP of my provider? This smtp server needs user and pass.

Thanks in advance for all!!

[abhiz]

please post the error that you are getting while sending email

[Firstime]

Sure!!

When I send an email from firstime@myisp.com to firstime@myisp.com I receive an email erro:

Mail delivery system.
This is the mail system at host mail.emailzimbra.net.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The mail system

<firstime@myisp.com>: host smtp.myisp.com[xxx.xx.xxx.xxx] said: 550
<firstime@mail.emailzimbra.net>: Sender address rejected: Domain not found
(in reply to RCPT TO command)

[Fox_sibirsky]

MX-record is coorect?

i'm use 1 accounts for 1 physical user, and multiple domain.
Inside domain @zimbra.isp.com
Outside domain @isp.com
Domain @isp.com is alias for local domain @zimbra.isp.com

source documentation: Managing Domains - Zimbra :: Wiki