I have installed Zimbra, and it works fine.
My Linux home PC has been configured to connect to my POP & SMTP.
My wife's Windows PC (older OS version) also connects to read/send her email.

Another person's email works via the web interface, but they can not correctly set up their computer's email program (outlook) to work for sending emails.

I have used my wife's computer and setup successfully their email - so i know the server/email/username/password/send/recieve works. It just does not work on their computer. I noticed their computer's OS (windows) is more recently updated.

I have noticed, what i believe is the key, that on my wife's pc, the first time you try to send/receive it asks if you want to trust the certificate, and on the other computer it does not.

I have followed the wiki for setting up a self cert and went through it with no problems.
SSL Certificate Problems - ZimbraWiki


Settings for both accounts to send/receive in OUTLOOK:
- receive: port 110 with no encryption (works fine on both computers)
- use SSL port 465 to send (SMTP)
- not using SPA
- requires SMTP authentication to send (checked)

I think the issue is with the other person's Window's configuration, but I've tried to find what setting would cause this. Does anyone know where I might look to change the settings?
Possibly I have messed up a setting in Zimbra...

Zimbra Settings:
MTA tab: checked- enable auth, notchecked-TLS-only
(for both global settings, and the specific server)

If I have missed posting some vital piece of information, please let me know.

Thanks for any help.