Hello there,
Go to Start and open Mail. Select Manage Accounts and select your email account. Select Change mailbox sync settings > Advanced mailbox settings. Confirm that your incoming and outgoing email server addresses and ports are correct.
Meanwhile, you may try to re-add your account and check if the issue persists.
https://support.office.com/en-us/article/set-up-email-in-the-mail-app-for-windows-10-7ff79e8b-439b-4b47-8ff9-3f9a33166c60?ui=en-US&rs=en-US&ad=US
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