For example, several ISPs have increased their email security settings which could require you to enable SSL or make port changes.
Also, sometimes they have merged with other ISPs and decommission the old account settings over time requiring you to make changes.
When you are deleting reminders from Exchange accounts, choose your Mailbox name.
When Outlook worked before and you’re suddenly presented with send/receive errors, it is still good practice to verify your account settings and make sure that they are current.
When cleanreminders doesn't work, look for the appointment the reminder belongs to and delete it.
When you can't find the appointment, you need to use MFCMAPI to browse "inside" the message store and delete the reminders.
If you can't find it, you'll need to use MFCMAPI to delete the reminder.
Download MFCMAPI Please note the steps are slightly different when you use a pst file or Exchange mailboxes and may vary slightly with newer versions of MFCMAPI.