I am trying to add my charter email account to my macbook air.

... and I understand that this is not working for you.

The only other thing I can think of is to try the following when you add the Charter account to Apple Mail:

• From the Apple Mail menu, select Mail > Add Account...
• Select "Other Mail Account...," and then, select Continue.
• Enter your email address and password ... but BEFORE clicking on "Sign In," hold down the Option key, and then, click it.
• You should be given the opportunity to enter both the account type and the servers.

If it fails to go on to this page, then there is something wrong with your Mac's user profile that is preventing this from happening. At this point, I would suggest creating a new user account on your Mac. Sign out of your current account, and then, sign in with this new account. Open Apple Mail, and then, try adding your Comcast account to it.

I am assuming that you are having an issue adding your Charter email account to the macOS Mail app on your Mac ... correct? If so, can you successfully access your Charter email account via a web browser from this same Mac?

Yes I can access it via a web browser

Ok, then we know, at least, that you can access your email account with your user credentials (email username & password)

Let's verify that you are entering the correct email server information when you set up your Charter email account in macOS Mail. Use the following link and just enter your Charter email address: Mail Settings Lookup - Apple Support. This should provide you with the proper settings to enter in macOS Mail. Please post back your results.

however my files are missing from the web email. Charter tells me that they dont transfer to the web if they were created in Outlook

Do you know if your Charter email is an IMAP or POP3 account? These perform differently when retrieving emails from Charter's email servers. The fact that they were created while using the Outlook app is irrelevant.

Apple tells me the account can't be set up because Charter's server is not responding to the request to verify the account.

That may be possible. However, what is happening behind the scenes when you add an email account to macOS Mail, is that a message is sent to the email host server with your user credential to verify that the account is active. Something obviously is going wrong at this point.

One thing to try is to use the Mail Connection Doctor and see what it tells you.

Ref: Use Mail Connection Doctor - Apple Support

Charter uses different servers for the iPhone and the iPad and I have been able to set up my email on those devices. The problem is with my MacBook Air. Charter uses a different server for that and that is the one that is unresponsive.

I find that extremely odd. For example, when you enter your Charter email address in Mail Settings Lookup link that I provided earlier, I would expect that it would result with two servers: an SMTP server for sending (outgoing) emails and an IMAP/POP3 server for receiving (incoming) emails. Even if you have multiple email accounts with Charter I can't imagine why they would require different servers than these.

I'm curious, what were your results when you entered your Charter email account in that link? Is this the same email address that you use with your iOS devices?

Thanks for reporting back. The Mail Settings Lookup is not 100% flawless, but it should be able to determine the email servers for most, if not all, major email providers ... so I'm a bit surprised that your Charter email address did not come up with the Charter servers. Charter uses the same email servers for both mobile and non-mobile devices.

Charter's email domain is: @charter.net. I would expect then that your email address would be something like: YourUsername@charter.net. If this is correct, then the proper servers would be:

IMAP

mobile.charter.net

Port: 993

SSL: Yes

SMTP

mobile.charter.net

Port: 587

SSL: Yes

Ref: Adding a New Email Account in Apple Mail - Spectrum

You are very welcome! I’m glad you got it worked out...