To enable encryption (SSL/TLS) in Mozilla Thunderbird, proceed as follows:

  • Open Mozilla Thunderbird.

  • Press the Alt key.

  • Click Tools > Account Settings in the menu bar.

  • In the navigation bar on the left, click the arrow that appears in front of the account name.

  • Click Server Settings in the navigation bar on the left.

  • In the Security Settings section, select SSL/TLS in the Connection Security list.

  • In the Authentication method list, select Normal Password.

  • In the Server settings section, in the Port: field, enter port 993.

  • In the navigation bar on the left, click the arrow that appears in front of the Outgoing server (SMTP) menu item.

  • Double-click on the outgoing mail server smtp.ionos.com.

  • In the Connection Security list, select SSL/TLS.

  • In the Authentication method list, select Normal Password.

  • In the Port: field, type port 465.

  • Click OK.