Some possible symptoms may include

• Original email messages in an email thread appear to be missing. You can see that your email address was included in the original email message, but you only see the latest email message in the thread in your mailbox.
• Email messages appear to be missing.
• There seem to be large gaps in dates and/or times in your mailbox; you should have received messages between these time frames.

It is possible that you have conversation grouping enabled for your mailbox. Conversations will group all messages in the same thread with the same subject line as one line item withing your inbox.

If you are fine with this grouping, there is no action needed. If you would prefer each message to show as a separate line item within your inbox, disable conversation grouping in Outlook on the web.

Customer Issue 659924