Instant message delay

Good afternoon! Our team is kicking around the thought of using Glip to communicate throughout our organization. I installed the Outlook plugin (Outlook2016) which seems to be working perfect except for a pretty hefty delay delivering (instant) messages. Sometimes it might send right away but the longest we have seen was as long as 15 minutes. Wondering if this is a known issue or something we may be able to configure differently to help? Thank you, Nick