Bon, je ne sais si c'est ca le problème ou pas, mais j'ai creusé un peu plus loin pour toi et dans une page d'une autre école, il semble dire qu'ils ont le même problème.
Voici un extrait de ce qu'ils disent. Désolé c'est en Anglais, par contre, je vois que tu es bilingue! :-)
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"Why can't I send email with Outlook Connector after installing Symantec AntiVirus?
If you are using the Exchange mail system these instructions do not apply.
To workaround this problem, either turn off Internet E-mail Auto-Protect and avoid the problem, or configure both the Connector and SAV differently.
Internet E-mail Auto-Protect is not enabled by default on the managed Symantec AntiVirus client. However, during the client setup wizard, there is the option to turn it on. If you'd like to turn it off, from the Symantec AntiVirus Client program, go to Configure > Internet E-Mail Auto-Protect and uncheck the box next to Enable Internet E-Mail Auto-Protect.
If you want to use Internet E-mail Auto-Protect with Outlook Connector, you must change the SMTP port numbers to 587. You do this both in the Mail Control Panel applet as well as in the Advanced settings for Symantec AntiVirus Internet Email Auto-Protect.
To change your SMTP port number for Outlook Connector, see the section on Outlook in the document Changing Your SMTP Server Port.
To change the Symantec AntiVirus port number for SMTP, go to Configure > Internet E-mail Auto-Protect > Advanced. Under Server port numbers, change Outgoing (SMTP): to 587.
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Je sais que ça indique Outlook, mais devrait être le même cas pour tous les clients...
Laisse-nous savoir si ca aide...