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Office 365 IMAP and SMTP Settings

CSU's Office 365 tenant supports secure IMAP connections for accessing a mailbox and authenticated SMTP to send e-mail from Office 365. The information below is intended to act as a reference when configuring an e-mail client and can be used to specify the appropriate values in the "Account Settings" (or similarly-named) section of your e-mail client for incoming and/or outgoing e-mail. If you have questions regarding the setup or configuration of your e-mail program, please consult your local IT support staff or contact

Secure IMAP Settings (Incoming Server Settings)

  Email Address: (or for secondaries)
  Incoming Server:
  Incoming Server Username:
  Incoming Server Port: 993
  Incoming Server Connection Security: SSL

Office 365 SMTP Settings (Outgoing Server Settings)

  Outgoing SMTP Server:
  Outgoing SMTP Server Port: 587
  Outgoing SMTP Server Username:
  Outgoing SMTP Connection Security (if applicable): STARTTLS or Auto

Note: ACNS supports a locally hosted smtp service ( for use with on campus web apps, software applications, printers, scanners, etc. Please contact the Central IT Help Desk for configuration details for that service.

Configuring Thunderbird (Version 31.3)

Note: An IMAP e-mail client only provides access to e-mail. For calendaring purposes, including creating and responding to meeting invitations, you must use Outlook installed on a PC or Mac or log in to the Office 365 Portal.

The following steps outline the process you would follow to configure Mozilla Thunderbird version 31.1 to connect to your CSU Office 365 account. Actual steps may vary depending on the version of Thunderbird you are using.

  1. Launch Thunderbird mail client. If this is the first time you have launched Thunderbird, select whether you want to use Thunderbird as your default mail client. If so, select "Set as Default." Otherwise, choose "Skip Integration."
  2. Do not choose to set up a new email address. Press the "Skip this and use my existing email" button: New email address screen showing skip button
  3. If the wizard does not appear automatically, go to "Tools" > "Account Settings" > "Account Actions" (button) > "Add Mail Account" from within Thunderbird. If you do not see the "Tools" menu, right-click the top of your window and select "Menu Bar."
  4. On the resulting Mail Account Setup wizard window, enter the requested information as shown below and click "Continue."
    Your Name: First Last
    Email Address:
    Password: eID Password
    Remember Password: Checked
  5. Thunderbird will attempt to automatically configure your incoming and outgoing account settings. When it completes and fails to automatically configure the process, click the "Manual Setup..." button.
  6. From the Account Settings window, click "Server Settings" under the account
  7. Set/Verify the following settings for the incoming IMAP server:
    Server Name:
    Port: 993
    Connection Security: SSL/TLS
    Authentication method: Normal password
  8. Set/Verify the following settings for the outgoing SMTP server:
    Port: 587
    Connection Security: STARTTLS
    Authentication Method: Normal password
  9. Click Done to apply modified Server settings (see screenshot). Mail account setup window example