I believe I have discovered a bug with Outlook from Office 365 (desk application). I have set my default reminder for meetings at 5 minutes. Meaning, for every meeting in my schedule, I receive an alarm 5 minutes before the event.
This works fine for the meeting I create. But it doesn't work for what is already scheduled in the calendar (already scheduled, but have not yet happened). It doesn't work either for meetings that others create.
I have tested it with another colleague. He said he hasn't noticed it. However, maybe it is happening and never realised it because he wasn't paying attention. SO, I created a meeting with him for 20 minutes later, with a reminder of 15 minutes. He accepted it before the 15 minutes window. At 15 minutes, I received my own reminder (everything in order here). However he didn't. He received it at 10 minutes. Which doesn't make any sense, because HIS default setting is at 5 minutes. Where the f*** does the 10 minutes come from?! (Not angry, just... really surprised and saying it with a lot of expression)
I didn't signaled it before because of a previous bad experience with Microsoft support, as I strongly believed the parameter was coded that way and it was some sort of design flaw. However, this comes prove this isn't intended that way. So here I am!