Mail app not sending Gmail messages on macOS

Hi everyone!

I’m having an issue with the Mail app on my Mac. I have multiple Gmail accounts added, and I can receive emails normally, but I cannot send messages from one of them. When I try to send an email, I get a popup saying “Cannot send message”, and it asks me to select a different outgoing mail server.

In the SMTP list, my Gmail SMTP servers appear, and is Online. Even when I choose “Always Use This Server,” the message still does not send.

What I’ve already tried:

• Removing and re-adding the Gmail accounts
• Checking SMTP settings (smtp.gmail.com, SSL, ports 465/587)
• Resetting Mail settings
• Restarting the Mac

All Gmail accounts work normally on the browser and on my iPhone — the problem is only in the Mac Mail app.

System Info:

• macOS version: Tahoe 26.1
• MacBook Air M4

If anyone has seen this behavior and knows how to fix this issue, I would really appreciate guidance.

Thank you!