Unable to send emails via Outlook when in Colorado?

I've used Cox email with Outlook since the 1990s.  The last two years I have had a problem in which Outlook will not communicate with the Cox server when I travel, especially, when I'm in Colorado.  Outlook receive email, but I can't send any emails from Outlook.  Cox is working as I can send email from my cox webmail account.  How do I fix Outlook as that is my primary program?