Retain 3.5.1 and later
Google Apps Module
My Google Apps archive job was running really fast - at 11 messages per second - and now it is crawling at 0.03 messages per second. What is happening?
Retain connects to Gmail through the Gmail API. This access is super fast; however, Google sets a connection quota on a mailbox, and if that gets exceeded, it will throw an error at Retain and refuse the connection.
When Retain gets that error, it makes a few attempts to reconnect. If those attempts fail, Retain will revert to an older iMAP technology, which Gmail supports. Historically, iMAP access is on the opposite end of the performance scale from the Gmail API - it is super slow.
Make sure you run your jobs at night. You may want to adjust your job schedule to start in the middle of the night.