Also, App Engine is integrated with both Sendgrid and Mailgun, and we strongly recommend using these if you're planning on sending larger quantities of mail:
Whether it's your outgoing spam filter that's overzealous, or if a datacenter is on fire is irrelevant. Your infrastructure stopped doing what your docs said it would.
Paying customers like myself have apps running on your infrastructure. Your infrastructure stopped delivering the exact same emails that it had been delivering for years. It did this without notification and without triggering any errors.
Approximately 35 quote requests that should have been delivered have disappeared into thin air. You've cost me money, and I'm disappointed to find out that you'd been notified of this issue weeks before it began affecting me.
At the VERY least you could have easily set up a gmail account and sent them from smtp. Choose the right tool for the job.
I partially agree with this - dedicated email services have a higher deliverability rate than a random web server, especially a cloud-based server that might be using an external IP that was previously used to send spam. However, I can understand the parent poster being annoyed that their emails were being delivered one day, and not the next, without any changes on their end.
> At the VERY least you could have easily set up a gmail account and sent them from smtp. Choose the right tool for the job.
This is absolutely the wrong tool for the job. You should not be using a Gmail account to send out automated emails that you care about.
Agreed, but better chance of delivery than directly from the server.