First try all variants in your browsers: http://stamps.com
. The first three should be redirected to the last one.
Try to determine the IP addresses of the web site in command line:
If you get a "Non-existent domain" message then it's a DNS-related error. If the IPs you see are different from those above, your OS still has old DNS records in its cache (somehow).
You have the curl tool available in Windows 10 command line. Try to get some response from the web server:
curl --header 'Host:www.stamps.com' http://22.214.171.124
curl --header 'Host:stamps.com' http://126.96.36.199
curl --header 'Host:stamps.com' http://188.8.131.52
A giant chunk of HTML code is supposed to be printed out after each command. If you get an error message, it means that the access path from you to the web server is blocked by some firewall.
I used the same command in the 'online curl' tool at https://reqbin.com/curl
since my Windows is No. 7, the one without curl.
Also, some DNS history is available at:https://securitytrails.com/domain/www.stamps.com/history/a
- the IP for www. stamps.com hasn't changed in more than a yearhttps://securitytrails.com/domain/stamps.com/history/a
- new IPs for stamps.com since March 1st, 2021. This could be the root cause of your problem, maybe the IPs haven't propagated to every DNS server and DNS cache yet.
Oh, and thanks for stopping at TR and asking for help. I've learned some new useful things when putting all this together.