I will do dns at my registrer as I have my websiteThere is no telling. Most of the time it is within minutes and sometimes it is longer and there is always the potential for 72 hours but I have not seen that since the 90's.
Do the website will take time as A record and name server will update??
Also I want to receive answers from multiple experts ??What is it you need to hear? This is getting confusing. You said you did a migration to Microsoft365 (Formerly Office365) and that your website does not work. I gave you the potential reasons, either you do not have an A record pointing to your site or you have the A record pointing to your site but you do not have the webserver setup correctly Or you have a firewall issue if you can see the site outside of your network.
Ensure it is pointing to your hosting company IP address.
After migration did you reconfigure outlook?
Your internal domain name and external domain name is same?
How did you add domain to O365? Added manually or added by signing into your DNS registrar from O365?