Setting up an @ac-creteil.fr account on a desktop client is not limited to filling in server fields. The blockage occurs later, when synchronization fails without an explicit error message or when remote folders do not map. Here, we detail the real friction points that step-by-step guides do not address.
Port 993 blocked on establishment: diagnose before configuring
The IMAP/SMTP configuration for Créteil email is standardized: IMAP on port 993 with SSL/TLS, SMTP on port 465 (SSL/TLS) or 587 (STARTTLS). The identifier is the full email address, not a short login.
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The problem almost never comes from these values. In educational institutions, port 993 is often filtered by the proxy or network firewall. Outlook then displays a failure to connect to the incoming server, without specifying that the port is blocked.
Before any configuration, we recommend testing network connectivity. On Windows, open a terminal and run the command telnet imap.ac-creteil.fr 993. If the connection times out, the port is filtered and no Outlook settings will change that. You should then contact the digital reference of the institution or use webmail while waiting for the port to be opened.
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On a home network or mobile hotspot, this blockage usually does not exist. If the configuration fails under these conditions, the problem lies elsewhere.
For a complementary approach, you can set up Créteil email on Geekfinity by following the detailed procedure that covers the academy’s server values.
Configure Outlook with the ac-creteil.fr account without autodiscover
Outlook systematically attempts to automatically detect settings via the Autodiscover protocol. For academic addresses, this detection fails. The software then suggests an Exchange or Microsoft 365 configuration, which does not correspond to the infrastructure of the Créteil academy.
The only reliable method is manual configuration in IMAP. In Outlook (desktop versions), you must force advanced mode as soon as you add the account to access the incoming and outgoing server fields.
Values to enter in Outlook
- Incoming IMAP server: the academic server, port 993, SSL/TLS encryption, identifier = full address @ac-creteil.fr
- Outgoing SMTP server: same server domain, port 465 with SSL/TLS or 587 with STARTTLS depending on the version of Outlook
- SMTP Authentication: enable the option “My outgoing server requires authentication” with the same credentials as the incoming server
A common trap in Outlook 365 (the version integrated into Windows 11): the simplified interface does not always offer the manual IMAP mode. You then need to go through the classic control panel, “Mail” section, to add a profile with full control of the settings.
Check actual sending after configuration
Receiving messages does not guarantee that sending works. Test sending to an external address (Gmail, for example) immediately after configuration. If the email remains stuck in the outbox, the SMTP port is likely filtered or outgoing authentication is not enabled.
Thunderbird and Créteil email: remote folders and OAuth2
Thunderbird often automatically detects the IMAP settings of the Créteil academy via its ISPDB database. The initial connection works, emails arrive. The problem appears afterward.
Manually map IMAP folders
The Sent, Drafts, and Trash folders on the server do not always synchronize with their local equivalents in Thunderbird. As a result: emails sent from Thunderbird do not appear on webmail, and vice versa.
To fix this, open the account settings in Thunderbird, then the “Copies and folders” section. You need to associate each action (sent, draft, trash) with the corresponding remote folder on the IMAP server, not with the local folder created by default.
Authentication: normal password or OAuth2
Thunderbird offers two authentication methods. For @ac-creteil.fr accounts, normal password authentication remains the functional method. OAuth2 is not supported by the academic infrastructure of Créteil. If Thunderbird selects OAuth2 by default, the connection will fail without a clear error message.
In the settings for both the incoming and outgoing servers, ensure that the authentication method is set to “Normal password” or “Encrypted password,” never to OAuth2.
Activating the Colibris account: the forgotten step that blocks everything
Configuring an email client assumes that the @ac-creteil.fr account is active. This activation goes through the Colibris platform of the academy, in three distinct steps:
- Create the account on Colibris with the NUMEN or the information provided by the rectorate
- Validate the email address from the Colibris interface
- Log in for the first time on webmel.ac-creteil.fr to finalize the initialization of the mailbox
If this last step is skipped, the IMAP server refuses the connection from Outlook or Thunderbird, even with correct settings. The first connection must be made via webmail before any configuration on a desktop client.
We regularly observe this case with staff newly assigned to the Créteil academy, who attempt to configure Outlook before initializing their mailbox on webmail. The error message returned by the email client does not mention Colibris activation, making diagnosis difficult without knowing this sequence.
One last point to keep in mind: the password set on Colibris is the one to use in Outlook and Thunderbird. Any subsequent reset on Colibris invalidates the credentials stored in the email client, which will then request a new entry without always explaining why the old password no longer works.