All of my email since May 5 is missing except for what arrived in the last hour.  I'd really like to get it restored.

Yesterday I experienced the same exact problem, except I was missing all of my messages since May 10.  However, after a few hours they were restored.  I hope yours come back as well.   Here is my thread:  https://forums.xfinity.com/conversations/email/all-of-my-emails-from-the-past-23-days-have-vanished-from-my-account/647a79ce27f9157f6ffb8678

Hello @user_baadae. Were you checking the email in a client based platform or direct via web browser? Thank you for reaching out. 

Email is gone from Comcast Web based email, Outlook client and Apple mail client.  It appears some sort of "roll back" to May 5 has occurred on the Comcast server side. Some crucial messages are missing so please restore.  Thank you!

We can easily do a deeper dive.

Could you please send our team a direct message with your full name and full address? Our team can most definitely take a further look at this issue.

To send a "Peer to peer" ("Private") message:
Click "Sign In" if necessary
• Click the "Peer to peer chat" icon
• Click the "New message" (pencil and paper) icon
• Type "Xfinity Support" in the "To:" line and select "Xfinity Support" from the drop-down list which appears. The "Xfinity Support" graphic replaces the "To:" line