Email will not send !/2 the time.

Try setting up another admin user account to see if the same problem continues. Please post back on whether or not this worked. Also try the Safe Mode. Please post back on whether or not this worked.

Isolating an issue by using another user account 

Safe Mode - About

If it works in the Safe Mode, try running this program when booted normally and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor.  Please use copy and paste as screen shots can be hard to read. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown.

Etrecheck – System Information

If the log won’t post, try posting it in Pastebin and provide a link in a reply        Pastebin

Please paste the output configuration report of EtreCheck here, using the highlighted button to hold the pasted report:

This report will provide us with a hardware and software comfigurarion information.

Are you using any anti-virus programs or Internet blocking programs like Little Snitch?

Please post the EtreCheck data. That'll provide some details on the specific software and hardware configuration.

Beyond indicating that the network is partially working, search engine settings and usage are not relevant to sending mail via macOS Mail.app. Nor is Safari and Firefox usage. Nor is the Earthlink web mail interface.

Wi-Fi might or might not be an issue, as this could be a network configuration error, or a problem with the Wi-Fi hardware. Or a problem with the network, the network ISP, or the mail provider. These sorts of outages can be intermittent, or can be prolonged outages. This if Mail is indicating intermittent connectivity. If (just) Mail is offline for sending at all times, then that can also involve the local Mail configuration, SSL/TLS setting, username and password, and related server settings.

As for the Earthlink SMTP settings from the Earthlink mail FAQ:

I can receive email, but not send it. What should I do?

Check to make sure that your email program has the outgoing (SMTP) sever set up correctly.

The Outgoing SMTP server should be smtpauth.earthlink.net (same for all email addresses)

Put a check in the box for “My Outgoing SMTP server requires authentication” (or something similar) and enter your entire email address and password for authentication.

Set the Outgoing SMTP port number to 587. This is usually found under your email software’s Advanced Account settings section.

Apple buries the outbound SMTP server settings under the "Edit SMTP Server List" item in the SMTP server selection pop-up used in related versions of Mail.app.

One of the more common tests here is the Connection Doctor, though.

No none at all...I am using Firefox, but have tried safari, made no difference, tried different search engine, reset wifi but smtp keeps saying I am offline