New company took over and outlook now having issues

I was with Centurylink. They forced me to have Brightspeed. I was assured nothing would be affected. They were wrong. I have never used webmail and have always had my webmail forwarded to my Outlook that I had bought. Since Brightspeed has taken over I am having issues. My Outlook 2021 from Microsoft keeps synchronizing and I my emails either won't go out or take forever to come in or go out and it keeps saying synchronizing folders and I have no clue what that means and why today it started doing that. Brightspeed is no help. Centurylink helped me with the POP info to put in and swore there would be no issues but no longer will talk to me since they said I am a Brightspeed customer and I can't talk to anyone with Microsoft. I don't know why this suddenly started today and Brightspeed had no answers and basically just said good luck. I have work emails that I forward to my outlook so I can print to do my teleworking. It's been over 3 hours and I don't even know why synchronizing is or why it's doing this. HELP. I need it to stop doing that and for my emails to come and go quickly like they were doing yesterday. Any ideas or help anyone can give me.