Hi kkPaine,
Email clients such as the ones you use on your MacBook Air, iPhone, or other devices use the prescribed information from your email service provider to log into that account on your behalf, download new messages and send outgoing ones you've written, and sync changes such as deletions.
As you were able to correct the information on your Mac, it likely has the necessary information stored in terms on incoming account server (usually starting with IMAP or POP), outgoing server (beginning with SMTP as you noted), the required ports, security protocols, user name (commonly your email address but could be different) and account password.
Comparing that information to what your iPhone has stored using the steps in Change email settings in Mail on iPhone to ensure they match would be advised. Some email providers may require specific passwords to be used for account access, such as those described in Using app-specific passwords when attempting to check iCloud Mail on a non-Apple device or app. Your provider can tell you if this is required and how to create one if necessary.
Regards.