ahmedsa/jonson
This is sme server release 8.1
smtpsmarthost altawi.com.sa
Based on information in other threads that is your own servers domain name URL, you would use that to configure your email client when asked for SMTP server name & IMAP server name.
AFAICT it is NOT your SMTPSmartHost setting.
Your SMTPSmartHost setting (address of your ISPs SMTP server) should (apparently) be
smtp.awalnet.net.sa
that is what your ISP awal advised on their website tutorial.
Change that in Server Manager - Email panel, for Address of ISPs SMTP server
Your email may then send correctly.
To remove issues with Outlook 2007 client configuration, can you please use webmail to test sending & receiving of mail.
https://altawi.com.sa/webmaillogin as a valid user & try sending an email message to an external address. Please setup a free gmail account for yourself & send an email from sme servers webmail application to your gmail email address.
Testing that way will remove any issues with yahoo (who can be very fussy) & also remove issues with email client (Outlook 2007).
Once it has been proven you can send email from webmail satisfactorily, you can then troubleshoot Outlook 2007 configuration.
I would suggest to install Mozilla Thunderbird on a workstation behind sme server & use that to test your settings etc. Thunderbird is a very robust email client & is known to work well with sme server. Once you know Thunderbird can send & receive correctly, then you can troubleshoot Outlook 2007 issues.
At the moment you have multiple issues going on, so test & fix them one at a time using the software tools & methodology I have advised.