I cannot send an excel data sheet through my email and it says the name can't be matched to a name in the address list.

The error indicates that the email address being used cannot be resolved to a valid recipient in the address list, so the message cannot be sent.

Use these checks:

1. Verify the recipient address
   • In the To box, type the full email address (for example, name@example.com) instead of just a display name.
   • Make sure there are no spelling mistakes and that multiple recipients are separated by semicolons.
   • If the address still appears underlined in red or marked as unresolved, it cannot be matched and the message will not send.
2. Use the address book / check names
   • If using Outlook (including the light version), after typing the name, use Check Names.
   • If no unique match is found, Outlook shows possible matches or leaves the name unresolved in red. Select the correct match from the list, or enter the full email address directly.
   • Email messages cannot be sent to unresolved recipient addresses.
3. Confirm the account and mailbox
   • This error can occur if the account is not associated with a mailbox, is hidden from the address list, or is misconfigured on the email server.
   • If this is a work or school account, contact the email/IT administrator to confirm:
     • The mailbox exists and is active.
     • The mailbox is visible in the address list.
     • The username and domain being used are correct.
4. If using a connectivity test tool
   • When using Microsoft Connectivity Analyzer or similar tools, ensure the username and domain are exactly as provided by the administrator. An incorrect username or a misconfigured mailbox will cause the same “name could not be matched” error.

If, after entering the full, correct email address, the recipient still shows as unresolved, the issue must be fixed on the mail server side by an administrator (mailbox creation/visibility or permissions).

References:

• Address Book in the light version of Outlook
• The user name provided could not be matched to a name in the email server's address list
• Name Could Not be Matched to a Name in the Address List