Step 1: From the File menu, select “Info” and choose “Account Settings.”
Step 2: Select your Email account and click the “Change” button.
Step 3: Click the “More Settings…” button in the bottom-right corner of the E-Mail Accounts window.
Step 4: In the Internet Email Settings window, click the “Outgoing Server” tab.
Step 5: Check that the box next to “My outgoing server (SMTP) requires authentication” is checked and “use same settings as my incoming mail server” is selected.
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