One of the first questions I'm asked when I travel and someone finds out I support Microsoft Outlook, is:
How do I send mail from the hotel?
They can download their email just fine, but replies won't send and they have no idea what's wrong.
This is usually the result of authentication issues. In order to prevent strangers from using their SMTP server to send spam, many ISPs require users to authenticate when they try to send email while accessing the server from outside the network. In many cases, users will also need to use a different port number and may need to use SSL.
Check Outgoing Server Authentication
To check or change the outgoing server authentication, you need to open the Account settings dialog. In Outlook 2010 or Outlook 2013, this is on the File tab, and on the Tools menu in Outlook 2007 and earlier versions.
After opening the dialog to the list of email accounts, double click on the email account then click the More Settings dialog and select the Outgoing server tab to check the authentication settings.
Enable My outgoing server (SMTP) requires authentication and select Use the same settings as my incoming mail server. These settings will often work both at home and when traveling.
You'll also want to check the port and SSL settings on the Advanced tab. Commonly used port numbers are 587, 465, and 1025 but if these don't work, you'll need to check your mail providers support pages for the correct port number. You may also need to select SSL or Auto for encrypted connections; again, this information should be on your mail providers support website.
Once you make these changes, you should be able to send email from home, coffee shops, or hotels.