If you're using a legacy email client, you may want to upgrade your IMAP host, which will allow you to access your emails from other networks. However, if you're using an older email client, it's advisable to use a third-party email client instead of AT&T's own. It will ensure that you have the fastest access to your emails. It's also worth notifying your service provider to update your email clients.
See also - https://www.businesslars.com/2022/02/16/what-is-att-email-server-settings/