Configure TLS for Microsoft Outlook Email


This article assumes that you already have Outlook configured as the email client for your Dido Internet email address. For help setting up Microsoft Outlook as your email program, please refer to this help document.

This article explains how to enable the Transport Layer Security (TLS) protocol for the Microsoft Outlook email program. Enabling TLS in Outlook will improve the security of your email communication by encrypting the way Outlook communicates with Dido Internet’s email servers, and is recommended for all users.

TLS is the successor to the Secure Sockets Layer (SSL) protocol. Outlook can be configured to work with either, and both will provide increased security. However, TLS provides some enhancements over SSL.

This documentation uses screenshots from Microsoft Office Outlook 2007 & 2010 for Windows. However, the procedure is similar for enabling TLS/SSL in newer versions of Outlook.

Enabling these security features in Outlook requires you to change two account settings:

  • IMAP server settings for incoming email. The Dido Internet IMAP server uses the SSL protocol, and
  • SMTP server settings for outgoing email. The Dido Internet SMTP server uses the TLS protocol, the successor to SSL.

Enabling TLS

With your Outlook client open, select Tools from the main menu. Then select Account Settings… from the drop down menu. See Figure 1.

Outlook Account Settings

Figure 1


This will open up the Account Settings window. If you have more than one email account configured, make sure that your Dido Internet account is selected. With your Dido Internet email account highlighted, select Change. See Figure 2 below.

 Figure 2


This will open another window called “Change E-Mail Account“. Click More Settings…. See Figure 3 below.

 Figure 3


This will open another window called Internet E-mail Settings. Click the Advanced tab. Look in the section called Server Port Numbers. In the drop down menu under Incoming server (IMAP), select TLS from the list of options. The port number should be set to 993.

Then, in the drop down menu under Outgoing server (SMTP), select TLS from the options. Your outgoing server port number should already be set to 587, but if it is not type “587” in the Outgoing server (SMTP) field. See Figure 4 below.

Figure 4

Click OK to close the Internet E-mail Settings window. Close the Change E-mail Account window. Click Close to close the Account Settings window.

You have now configured the Outlook client to use TLS. If you wish to ensure that your settings are configured correctly, you can send a ‘test’ email to yourself. If you do not receive the email, make sure you followed the above instructions correctly, specifically the instructions for port numbers. If you are still experiencing difficulty, please contact the Dido Internet Help Desk