Gmail API: How to fix “Requested entity was not found” problem

This blog post is totally technical and just here to help fellow developers who might encounter the same issue.

If you are looking to hire a python developer, check out this outsourcing firm.

Problem

When working with the Gmail API to import messages, you first get a list of messages (with their associated ids) and then use those ids to get the email’s data, like this:

1. List messages to get message_id's
2. Get message using the message_id
3. Do something with the message

But sometimes, when you call the Gmail API with a message id you just fetched using the list() method, you get an error saying: Requested entity was not found.

How come Gmail can’t find a message it just told you exists?

Especially when the message actually exists! You can use the following link to see if one of your message exists using the message_id:

https://mail.google.com/mail/u/0/#inbox/<MESSAGE_ID>

If the message does not exist when you search for it using the link above, then it actually does not exist (like a draft that was deleted)

Solution

The id of a message actually seems to change in some cases - not that immutable. I haven’t fully investigated as this is out of scope but when a message gets a reply, it moves from being a simple message to being a thread - and in that case, sometimes the id changes.

When you get a list of messages, take the message id and the thread id.

If the message.get() method from the API doesn’t work with the message id, use the threads.get() method (documentation here) to get the updated message id and retry to get the message with that new id.

This will solve it! To summarize:

1. Get message and thread ids using the messages.list() method
2. Try to get the message using the message id
3. If it doesn’t work, get the new message id using threads.get()
4. Try to get the message again with the new message id

Hope that helps!