What is throttling?

Throttling is a security mechanism that keeps a server healthy and responsive. It is called "throttling" because it limits the work load coming through the server by regulating network traffic and minimizing bandwidth congestion. As a result, you may experience slow Internet and performance speeds.

Throttling is a general condition that all Microsoft Office 365 applications have to deal with and it is not something that can be affected or changed through configuration or regular troubleshooting.

Microsoft offers only a limited amount of bandwidth to each of their Office 365 or OneDrive customers and applications installed by those customers cannot go beyond those limits. Allocation of bandwidth is based on the number of licensed users on the platform.

Can I do anything about it?

If you experience slow performance in Keepit, please ensure that you are not running other data intensive solutions against your Microsoft Office 365 tenant, such as synchronization or secondary backup services. 

If this is not the case, then you can have Microsoft temporarily raise your throttling limits on Exchange.

Microsoft states the following:
Throttling limits can be raised by our support team for O365, we can request the following to be raised:
EwsMaxBurst : Unlimited
EwsRechargeRate : Unlimited
EwsCutoffBalance : Unlimited
(And highest limits available for EWSMaxConcurrency)

This is a standard procedure, and you can contact Microsoft support to get it changed. Typically for 90 days. These changes only affect Exchange, not Sharepoint, OneDrive, or Groups.