I’m working on a C# web application and need to send emails to multiple recipients using System.Net.Mail library. My code works fine when I send to just a few people, but problems start when I try to include around 30 email addresses in the recipient list.
Whenever I attempt to send to this many contacts, Gmail blocks the message and shows an error about the message being rejected. After this happens, my account gets temporarily suspended from sending any emails for about 24 hours.
What’s the best approach to handle bulk email sending through Gmail? Are there any settings I can adjust or should I look into different email services for this type of functionality?
Gmail caps bulk emails pretty hard - you’re probably hitting their limits. Standard accounts max out around 500 emails daily, plus there’s limits on recipients per message. Cross these thresholds and Gmail’s spam filters kick in, blocking you temporarily. I ran into this exact problem building a notification system. Switching to dedicated services like SendGrid or Amazon SES solved it completely. They’re built for bulk email and give you proper delivery tracking. You could try smaller batches with delays if you’re stuck with Gmail, but it’s unreliable - they’ll still flag suspicious activity. For serious bulk emailing, just move to a specialized service. It’s worth the switch.
totally get ur pain! i had the same prob with my emails too. try using BCC to send to many without showing all the addresses. also, dont forget to set up app passwords - way safer. but if issues persist, it might just be better to switch to a service like Mailjet; they really help with sendin lots!
I’ve hit this exact problem building client communication features. Gmail treats 30 addresses in one message way differently than individual sends - it triggers their bulk detection almost instantly. Gmail’s SMTP just isn’t built for app-level bulk sending, even though the limits look fine on paper. What worked for me: queue individual emails with random 2-5 second delays between sends. This mimics how people actually send emails and cuts detection way down. You’ll still need to watch your daily volume though. For production, I switched to Mailgun - way better deliverability and proper API integration. Their auth setup is cleaner than other providers, and the C# SDK drops right into existing System.Net.Mail code. Cost difference is nothing compared to the reliability boost.