Windows Live Mail 2012

Op. system: Windows 10

error message:

An unknown error has occurred.

Server: 'mail.charter.net'
Windows Live Mail Error ID: 0x8007007A
Protocol: SMTP
Port: 25
Secure(SSL): No

I have tried various suggestions from the forum but nothing works.

Do I have to change to another email program?

Receiving email and sending without attchment are OK.