my mail is not synchronizing with icloud; the activity screen keeps on showing "moving 1 from 80

Are you running any anti - virus programs? Using a VPN?

If the above doesn't work, try the Safe Mode.

Safe Mode - About.       

If it works in the Safe Mode, try running this program when booted normally and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor.  Please use copy and paste as screen shots can be hard to read. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown. If the log won’t post, try posting it in Pastebin and provide a link in a reply. After pasting the report in a PasteBin page, go to the top of the page, and copy the address in the URL bar. Paste that in a new reply.        Pastebin.    

Etrecheck – System Information.      

Web site version if required.  https://etrecheck.com

Create a new test user account https://support.apple.com/en-in/HT204443

And then configure mail accounts https://support.apple.com/en-in/guide/mail/mail35803/mac