Send Email with Attachment in ASP.NET MVC (.NET 10) – Gmail SMTP | No NuGet Packages

Send emails with attachments from ASP.NET MVC using Gmail SMTP – zero third-party libraries. No MailKit. No NuGet. Just pure .NET 10 and a properly configured Gmail account.

⚠️ The #1 mistake developers make: using their regular Gmail password. Google disabled "Less Secure Apps" in 2022. You NEED an App Password.

✅ In this video:
- Enable 2-Step Verification on Gmail
- Generate a 16-character App Password
- ASP.NET MVC project walkthrough (built with Cursor)
- Send emails with file attachments
- Fix common authentication errors

🔧 What you'll learn:
- System.Net.Mail with SmtpClient
- Gmail SMTP settings: smtp.gmail.com, port 587, SSL enabled
- IFormFile for file uploads in MVC
- Async email sending without blocking UI

❌ Common Errors & Fixes:

Error: "Authentication failed"
→ Fix: Wrong App Password. Regenerate it.

Error: "The SMTP server requires a secure connection"
→ Fix: Add EnableSsl = true

Error: "Mailbox unavailable / Rate limit exceeded"
→ Fix: Gmail limit is 500 emails/day. Wait and retry.

Error: Attachment too large
→ Fix: Gmail max attachment size is 25MB.

📂 Project built with: Cursor, VS2026, .NET 10, ASP.NET MVC

🎯 Why this works:
Gmail requires OAuth2 or App Passwords for SMTP. App Password is the simplest method for internal tools, testing, and automation scripts.

⚠️ SECURITY WARNING:
Never commit App Passwords to GitHub. Use User Secrets, Environment Variables, or Azure Key Vault in production.

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👍 Like this video if it saved you hours of debugging.

💬 Comment "APP PASSWORD DONE" when you get it working!

📈 Next video at 100K views: HTML emails with inline images using pure .NET

#ASPNETMVC #DotNet10 #GmailSMTP #AppPassword #CSharp #SMTP #EmailAttachment #DigitalTechJoint #DotNet #MVCCore #VisualStudio2026 #CursorAI

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