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According to machine translation, your question is:
Subject: Exchange mail address problem on outlook
Body: We've upgraded our OVH email addresses to exchange and since then the addresses no longer work (no reception and no transmission). How can we resolve this situation as quickly as possible?
If there is any misunderstanding, please feel free to point out.
If the issue is Outlook cannot connect to Exchange server, please make sure you have created an A record or CNAME record in public DNS or your internal network to point autodiscover.domain.com to the ip address or server name of the Exchange server.
If you are using Exchange Online (Microsoft 365), please refer to this link:
External DNS records required for email in Office 365 (Exchange Online)
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