Sync Performance

For most users, particularly heavier users, sync performance is important in an email application. Outlook 2016 went about syncing in a different way than Outlook 2011 does. First, 2016 prioritizes what it needs to sync based on what it thinks you, the user, wants. For example, if you click on a folder, that becomes the priority to sync. Click on several folders? It will sync them in what it believes is the best priority.

Within a folder, Outlook 2016 uses a three-pass method: grab the headers, grab the message text, and finally, grab the attachments. If you click on a message, that message will become the priority to sync first.

We wanted to give you an idea of a real world, larger sync. For each of four types of accounts: local Exchange, local IMAP, Office 365 Exchange, and Gmail, we had a set of folders: one with 5000 messages, and three more folders that had about 600 messages each. The later set of folders was either no attachments, all with attachments, or a mix of messages with and without attachments. In all, about 7000 messages for each of four types of accounts, or almost 30,000 messages on this large, multi-account, real world sync.

Outlook 2016 was not just faster, but it synced all the messages, and got the job done in a 1/3 less time.


Figure 10: Sync Performance — Real World Test
(shorter is faster)

We also wanted to try tests that would reflect a solid amount of mail. For example, for a high volume user that hasn’t checked email for much of the day. To do this we created the three folder sets of about 500 messages. One had no attachments. One had a mix of messages with attachments. The third had messages that all had attachments.

For the initial sync, the folder went from empty to filled with these messages. We timed two things; when the messages were user interface responsive, and the total sync time. User interface responsive means that we could see the message in the list, click on it and work with it.

For the incremental tests, we added about 200 to the folder that had a mix of messages with and without attachments. The incremental messages were also a mix.

The following are what we saw for each of the four types of accounts: Local Exchange, Local IMAP, Office 365 Exchange, and Gmail. All had the same tests run as described above. All the charts have the same normalization scale, so that you can compare one type of email account to another.

One thing to note about the difference in the progress bars for Outlook 2016 and 2011: 2011 often downloads in batches of 20 messages. It does this to be “kind” to the server it’s talking to. You see 20, then another 20, then another 20, and so on until it’s caught up. Outlook 2016 also downloads in batches of 20, but the progress bar correctly shows the entire amount of messages to sync, not just the status within the current set of 20.