Why do we receive the "Unable to connect to mailbox" error when the Techmail utility attempts to connect to our Office365 mailbox?
Environment:
Office365-hosted mailboxes
Oracle B2C Service, All versions
Issue:
The 'Unable to connect to mailbox' notification is encountered when the Techmail-S utility attempts to connect to the mailbox.
Resolution:
Please find below the most common causes for the error message:
1. Verify that the POP server configuration is correct and perform the change if needed. Example Office365 POP server: 'outlook.office365.com'.
2. Verify that the SSL method used for this mailbox is 'Use POP3 SSL port' and perform the change if needed. Techmail can connect to an Office365 mailbox only on port 995. Connections performed on ports 110 (SSL method disabled or STLS method) will cause 'Error connecting to socket' errors within techmail utility.
3. Check the Office365 mailbox from Microsoft's end and make sure that the Office365 account has E-mail capability:
- Please use https://login.microsoftonline.com/ and log into the Office365 account;
- Once inside, go to My Account and then to Subscriptions;
- Verify that you have a working license to use Office 365's e-mail functionality.
Additional Information (Click the 
to expand this section for viewing.)
- Check if you are be able to access the web-mail of your Office365 account (once logged in, click the 'Mail' button; the link should be https://outlook.office365.com/owa/ ).
- Check within the Office365 account and make sure that Subscriptions does not show the below message:
4. For Office365 mailboxes still using Basic Authentication:
- Verify that the POP account and password are correct and re-type both in the mailbox configuration page in order to make sure that the utility uses the correct credentials when connecting. Ensure that the POP account password is not longer than 20 characters.
- Check whether Basic Authentication has been disabled within Microsoft Exchange and extend if needed:
Answer ID 11115: Office 365 Pop3 basic authentication deprecation
- If setting this up for the first time, ensure all steps were performed in setting this up using Answer ID 11864: Setting up App Registration for Office365 Mailboxes
- If Office365 OAuth was working previously and is now encountering errors check whether the Client Secret in Azure has expired and regenerate it. This then requires an update to configuration key CUSTOM_CFG_MAILBOX_OA_CLIENT_SECRET and clicking the Authenticate button for the mailbox to re-establish appropriate OAuth jwt access and refresh tokens.
