Hi Team, I am using Outlook 2013 pro plus with office 365 Email Service. My query is 

I flag emails as Flag and reminder to it. After perfect time time set as reminder the reminder window pops up correctly. I have multiple reminder set. so the reminder window has many emails with due dates and i dont dismiss them.

After some point of time Many of the emails from the reminder windows disappears.

I dont know the cause of it. does reminder window in outlook is sync with calender settings?

Is there any defualt time in the registry that causes my reminder window emails to disappear? i think emails which are there in reminder should be there intact until and unless i dismiss them.

Troubleshooting Which i had tried is 

Creating a new profile

Repaired the office

Ran outlook in safe mode

Ran the switch /resettodobar /ClearReminders

Set all COM Addins to disabled

Disable Hardware Acceleration

• Edited by Aquib Qureshi Friday, April 03, 2015 7:15 AM Update

- You should have tried /CleanReminders and not /clearReminders.

Hi

As per the information and details provided by you, to solve this problem, please follow these steps: -

If your reminder is not working properly, I would suggest proceeding in the following order: -

• First, check if the Reminders are enabled, and make sure the check-box in the Calendar section that is labeled Default Reminders is checked.

• In that same section, the Reminder time should be set to something reasonable, like 15 minutes.

• If that does not fix it, then exit Outlook and restart it from the command line with the Outlook/cleanreminders command.

Use Cleanreminders Switch

The easiest way to try to get rid of corrupt reminders is by closing Outlook and reopening it using the /cleanreminders switch. To do this, press Windows key + R to open the Run dialog. Type Outlook /cleanreminders in the field and press OK.

Make sure you have a space between Outlook and slash. Using Outlook.exe is optional just the program name should work.

A very few people will need to use the full path to Outlook.exe. Click Browse and look under C:\Program Files\Microsoft Office\ (C:\Program Files (x86)\Microsoft Office\ if using 64-bit Windows).

I hope this information will be helpful for you.

Thanks and regards