Redirecting constantly, Safari can't connect to server, mail issues

Most of the times, this is due to a proxy server setting applied on your computer.

Check your Network Settings.

1. Open System Preferences.
2. Go to Network.
3. In the list, select the network service you use—for example, Ethernet or Wi-Fi
4. Click Advanced, then click Proxies.
5. Normally, you should NOT be able to see any 'checked' on that list. Unchecked things that are checked (if there is any).

Hope this helps you out.

The cause behind these symptoms may likely be adware or malware, an answer

may be to get & use MalwareBytes for Mac. Then sort through items left behind

that MW/Bytes cannot change back to original status. ['fix after-effects']

• If Safari can't open the page because too many redirects occurred - Apple Support

https://support.apple.com/en-us/HT203370

• Fix after effects of adware on Mac device – Malwarebytes Support

https://support.malwarebytes.com/hc/en-us/articles/360047142133-Fix-after-effects-of-adware-on-Mac-device

• Safari - Official Apple Support

https://support.apple.com/safari

• Adware Removal Guild - theSafemac

https://www.thesafemac.com/arg/

• How to remove the after-effects of adware - Mac Malware Removal Help & Support - Malwarebytes Forums

https://forums.malwarebytes.com/topic/236261-how-to-remove-the-after-effects-of-adware

• Eliminated browser redirects and advertisements - theSafemac

https://www.thesafemac.com/eliminating-browser-redirects-and-advertisements/

[Use  Malwarebytes Anti-Malware for Mac. It may be necessary

to run more than one scan. When you no longer need MWB,

the utility can be uninstalled: Malwarebytes Uninstall]

Earlier removal method (manual) could be useful, the browser is affected.