If you have an email account from a different provider than Google or Microsoft, you are able to connect the email account with SMTP credentials.
In your LiveAgent account, navigate to Configuration > Email > Outgoing Mail accounts, and click on the "Integrate new email account" button.
In the left "Mailbox account" section, choose the "Custom mailbox" option to connect your email account.
On the next screen, fill up all the given fields. The correct SMTP credentials can be found in your email account settings. If you are unsure where the correct SMTP credentials to your email account are located, please contact the administrator of your email accounts or email account provider.
Finish the integration and your email account will be successfully connected with your LiveAgent account, so you can start sending replies to your tickets/emails through this mail account directly from LiveAgent.
Any further changes to the username, hostname, or port will require that the email account be removed and re-integrated from the start, read more here.
If you'd like to connect an account with 2-factor authentication enabled via SMTP, you'd need to create an application-specific password as explained here and use it instead when connecting the mail account to circumvent the 2FA.