Same situation for me. Have been on with tech. support a couple of times, actually got them to admit that they had the problem, but could not offer any time frame for a fix. I have been unable to send out mail from Outlook for over two weeks. Tried Thunderbird with the same issues. This is totatlly unacceptable performance from a company that charges me as much as they do for their services. Guess I am going to have to look at atlernative services
After two weeks, the outgoing mail problem was finally fixed in the Troy, NY, region.
I successfully sent messages back and forth to my home and business accounts using outgoing servers smpt-server.nycap.rr.com and mail,twc.com and well as the private server my business rents space on. No setting changes were made. If Spectrum tells you it's your problem, don't believe them.
Just don't expect it to stay fixed. This is a good time to migrate to another e-mail service, such as Gmail or Outlook.com and free yourself from the pain of Spectrum's inability to manage their e-mail servers and webmail.