I’m trying to set up Gmail push notifications for my web application and I’m running into some confusion. I understand the basic concept of creating a topic and publishing messages to it, but I’m stuck on the implementation details.
My main question is about handling email thread replies. When someone sends an email and receives a reply on that thread, how can I automatically detect this on my web server? I know I could poll the Gmail API periodically to check for new replies, but that’s not efficient.
I want to use push notifications instead, but the documentation is confusing me. In the watch method, we need to provide a user ID, but what happens if that user hasn’t subscribed to the topic yet? Will the notification system still work?
Can someone explain the proper flow for setting up Gmail push notifications to track email thread replies?
Gmail push notifications work on the entire mailbox, not individual threads. When you call the watch method, Google pings your webhook whenever anything changes in that user’s mailbox. The tricky part? Filtering what you actually want. To track thread replies, you’ll need to keep a list of thread IDs you’re monitoring. When your webhook gets pinged, it includes a history ID. Use history.list with that ID to see what changed, then check if those changes involve your tracked threads. For user auth - they must authorize your app before you can set up watch subscriptions. No auth = failed watch. Also, subscriptions expire after 7 days max, so you’ll need to renew them regularly.
Store the historyId when you set up your watch - that’s how you track changes efficiently. When Gmail hits your endpoint, compare the new historyId with what you’ve stored and use the API to grab just what’s changed. Way better than reprocessing everything.
Gmail API push notifications work per user. When you set up a watch, you’re subscribing to changes in that user’s entire mailbox, not specific threads. Each user needs their own subscription with their unique user ID. The user has to authorize your app first, or the watch won’t work. Your webhook gets notified about any email in that mailbox. Then you fetch the message details through the API and check the thread ID to spot replies. Subscriptions do expire, but this beats constantly polling for updates.