Overview
If you are using Google's mail service Gmail as an external mail source for M-Files and you are getting a connection error while connecting to the Gmail email server, a few settings should be checked in the Google account and M-Files before contacting M-Files support.
Note that Google has deprecated basic authentication for mail connections, so you need to use "Google Mail (IMAP4)" for service type instead of "Generic IMAP4" when defining connection to external mail source in M-Files Admin.
Solution
Please check the following points if you get an error stating that communicating with the mail server failed:
1. Double check that the client ID and the client secret are identical what is defined in the Google Cloud Console in the connection properties for external mail sources in M-Files Admin. See this document how to create the OAuth client ID and the client secret:
https://kb.cloudvault.m-files.com/Default.aspx?#3ECA226F-7B54-428B-B539-DE443E6134EC/object/8AC83C0E-69B9-43FA-B86A-2292EAB85DFB/latest
2. Make sure IMAP is enabled for the used mail account. Login to the Gmail account you are using for the external mail source connection with a browser. In the mail page select settings from upper right corner, tab "Forwarding and POP/IMAP" and "Enable IMAP".
3. Go to "Manage Your Google Account" page and select "Security" settings. Make sure "Use your phone to sign in" and "2-Step Verification" is set to off in the "Signing in to Google" section.
4. If all of the above are set as suggested and the connection is still not working, go to https://www.google.com/accounts/DisplayUnlockCaptcha and follow the steps on the page.
5. When defining external mail source in M-Files Admin, do not use too short delay between checks, as this may lock access to Gmail account. Values above 60 seconds should be fine.
