Cannot send email on MacBook Air since Golden Gate 27.0.1 update

The gold standard for fixing a recalcitrant email account it to remove the affected Account(s), and add them again.

Refer to If you can’t send or receive email on Mac - Apple Support, but be sure to follow all the preliminary steps first.

Email used to be simple...

Anyway the good news is that you can and should prevail upon Apple to help, not only because the onset of the problem appears to correlate with the macOS update, but also since your MacBook Pro is new. Support for new Macs is complimentary, regardless of the nature of the problem, and even if you are not using that new MBP at the moment. Yes Apple uses "AI" which is unlikely to succeed, and you will also need to endure the ignominy of having to explain removing the problematic email Accounts and adding them again according to their own Support documents didn't work. That will waste time (again) but such is the nature of the AI-dominated world in which we live.

He also instructed me to make several changes through terminal that just didn’t feel right.

That doesn't sound like Apple. In fact I have heard anecdotally that Apple Support representatives have just recently been prohibited from doing that due to the extremely likely possibility of a simple typo resulting in devastating consequences. As for Yahoo! / Comcast technical support, I highly suspect they will be out of their element diagnosing any Apple device concerns. I wouldn't trust them.

For now... can you log into your iCloud Mail Account through Safari, as suggested in the Support document I referenced, as follows from this excerpt?

For example, if using an iCloud Mail account, you can use iCloud.com to send and receive email.

That is a fundamental troubleshooting step, and it — should — work. You can do the same with Comcast / Yahoo! through their webmail interface (I believe).

Let me know what you determine.

In any event I think you should contact Apple using the Support link on these pages. Two aspects of your concern are likely to draw their attention — the fact you correlated it to a macOS update, and the fact it affects iCloud Mail. Apple will be less interested in Comcast / Yahoo.

I am also concerned about who you contacted and what they did that made things worse.

I was unsure whether I was communicating with a human or a bot.

That is becoming increasingly difficult.

In any event, several of the rep’s cut/copy/paste recommendations to be entered into terminal were rife with warnings. I proceeded against my better judgment with two suggestions, but refused to do the third.

That raises all sorts of red flags. You were wise to end that conversation. It's all the more reason you should contact Apple through their Support link (use no other) until you ultimately reach a warm-blooded human that can help. Yes I understand that takes persistence, but real human beings are becoming difficult to reach. Finding competent ones even more so. What I would expect Apple to do is establish a link with your Mac (with your consent of course) so that they can interact with you in real time, see what's going on, and direct you (through the use of a pointer on your screen) to perform certain actions that you understand and agree with.

Apple cannot and will not take remote control of your Mac. That's important. Never let anyone do that. The only exception would be if you were to physically drop it off at an Apple Store, which I know is not an option for you at the moment.

We could continue troubleshooting over this support site, but if the "gold standard" (as I call it) doesn't work then it suggests deeper problems. Whatever that unknown other rep's Terminal instructions might have been still concerns me. Let Apple get to the bottom of it.

Thanks for responding, but that’s the first thing I tried. I also spent over five hours online today with an agent who instructed me to do things that made things much worse! Bottom line … still can’t send emails🙁

I contacted them through what I believed to be an AI chat, but in hindsight think it was a real person. I wasted hours with one rep who instructed me to add a fake account and email to resolve the fact that my computer was “tangled” and blocking the connection. He also instructed me to make several changes through terminal that just didn’t feel right. Following that fiasco, when I tried to login again, my FAKE credentials appeared and my real login information was gone!

I later spoke to another rep who was competent and walked me through several hours of changes to fix the many problems created by the previous rep and helped to restore my account. At that point, he (rightfully) suggested that I needed a break, so I had a late dinner and went to bed. I’m not sure that I can waste another full day - but he said that I could continue the conversation with him when I was ready.

I just bought a brand new MacBook Pro but am working with my MacBook Air because I am out of town. This has been an absolute nightmare since I am an attorney and need to correspond to individuals with attachments, etc.

Oddly, I can sent messages with my iPhone, but it is too difficult to send the lengthy documents and correspondence using a tiny screen and keyboard. I am simply able to apologize and explain that I’m experiencing a glitch.

I’m rethinking adding Apple Care to my new Mac if that’s the “care” I’ll receive!

You are correct about the formidable invasion of AI. While dealing with the first rep, I was unsure whether I was communicating with a human or a bot. It was not until I spoke to the second rep and he made reference to “the person” who gave me incorrect advice that I suspected I might be talking to a human. To be honest, I am still unsure.

In any event, several of the rep’s cut/copy/paste recommendations to be entered into terminal were rife with warnings. I proceeded against my better judgment with two suggestions, but refused to do the third.

You are also correct about the Comcast/Yahoo havoc. I have yet to speak to a single rep of either entity that was adequately trained. In fact, I once spoke to an Apple rep (when I had Apple Care on my iPhone) who stated that he “wished he had an iPhone!”

Yes, I am now able to log into my all of my emails using Mac Mail, but I still cannot send any emails even though my Connection Doctor give me the green light?!?

I have been an avid Apple supporter since making the switch over ten years ago, but I am beginning to lose faith. Recently, I spent DAYS deleting 9,189 blocked emails - one by one - after reading online that there was no other “fix.” I’ve also been held hostage in group messages if one of the participants is an Android user. I am far from a technology genius, but I simply cannot imagine why one of the Apple “geniuses” haven’t corrected these glitches.

I know that I have a free year of Apple Care under my new MBP, but, given the “care” I’ve received lately, I’m not sure I’m going to renew before the expiration of my date of purchase, 

Again, I truly appreciate your input!

Who did you contact, and how? Phone, or...?