I’m trying to fetch multiple emails quickly using the Gmail API with the following function:

def get_mails(self, ids):
    """
    Retrieve multiple emails using batch requests.
    It's recommended to use a maximum of 20 in a single call.
    """
    batch = self.service.new_batch_http_request()
    mails_map = {}
    def callback(request_id, response, exception):
        if exception is not None:
            print(f"Error occurred for {request_id}: {exception}")
        else:
            mail_id = response['id']
            mails_map[mail_id] = response
    for idx, msg_id in enumerate(ids):
        batch.add(self.service.users().messages().get(userId="me", id=msg_id), request_id=str(idx), callback=callback)
    batch.execute()
    return mails_map

Currently, it takes about 20 minutes to fetch 10,000 emails, which is quite slow. I can’t fetch more than 20 emails at a time using batch requests, as it triggers rate limit errors. However, I can’t find any specific rate limit values mentioned in the Gmail API documentation for batch requests.

Is there a way to increase the number of emails fetched in a single batch request without hitting the rate limits? Or is there a better approach to optimize this process and speed things up? Any guidance would be greatly appreciated. Thanks!