E-mail issues with Apple Mail on Macbook

I’m trying to help my wife with a recent issue with e-mail on her MacBook. For context, her MacBook is a 2019 model running MacOS Sonoma 14.8.4 and her Apple Mail app is version 16.0. She has a Comcast e-mail account. We recently did some updates on her machine, and since then, she receives her incoming e-mails properly, but when she tries to send an e-mail, she gets a pop-up with a message that says “Cannot send message using the server Comcast” and the Apple Mail “Connection Doctor” advises that “Trying to log into this SMTP account failed. Verify that the user name and password are correct.” I’ve done that, and read several of the articles on the Xfinity site about setting port settings, etc. but I cannot find any place in the account setup screen to check or change these settings. When she logs in directly to the Xfinity e-mail page, she can send messages without issue, so I’m concluding that maybe something in one of the updates “broke” the Apple Mail app, at least as far as using with the Comcast server is concerned. Any assistance? Thank you!