0x800CCC0F – Email connection interrupted

An email program reports an interrupted connection to the mail server.

Do not factory-reset a router speculatively or indiscriminately disable Wi-Fi security or a firewall. Get permission before changing someone else’s network.

Check internet and the status of your email provider. Try its official webmail site.
Compare server names, ports and encryption with the current information from the provider. Do not use random values.
Two-factor login may require a current login method. Use the provider's instructions; do not disable account security.

Test after each step and stop when the issue is solved. Checkmarks are not permanently saved.