The Mail app doesn't sync new emails automatically, it doesn't sync even after clicking the sync icon. If the Mail app on Windows 10 is not syncing properly, you can try out one of the solutions given below to resolve the sync issue.
If the Mail app is not syncing the latest e-mail, the first thing is to open and check the sync settings.
To do: On Mail app, click Settings button. Click Accounts, and then click on the account name that has sync issues.
Click Change mailbox sync settings.
Under Download new content, select as items arrive from the drop-down list. Make sure the E-mail, Calendar and Contacts option are turned on under Sync options.
Click Done, then click Save to save your settings. Close the Mail app and launch it again.
This is useful if an app gets into a bad state and you want to delete its data and start over.
Step 1: Press Win + I to open Settings app. Click Apps option.
Step 2: Click on Apps & features, on the right side, find Mail app, and click Advanced options link.
Step 3: Click/tap on the Reset button under Storage usage and app reset. Click/tap on Reset to confirm.
When finished, follow how to setup Mail app guide to add your e-mail account.
If your Mail app is freezing or not working, check if your Windows 10 has all the latest Updates installed. If this does not help, uninstall and reinstall the Mail app as follows:
Step 1: Open PowerShell as an administration.
Step 2: In PowerShell windows, copy and paste the following command, hit Enter.
Get-appxprovisionedpackage –online | where-object {$_.packagename –like "*windowscommunicationsapps*"} | remove-appxprovisionedpackage –online
Step 3: To reinstall Mail app, you can download it from Windows Store.