Why are some relationship fields on a contact not populated?

Some of the contacts like Strongest Relationship, First Relationship, Latest Relationship and some others may not be populated on all contacts depending on how the contact was discovered. 

This can be due to a few reasons:

1. Statistics may not have been calculated yet - While processing emails for a single mailbox we calculate these statistics at the end of processing the mailbox. For a customer with 10 or more mailboxes connected we process statistics every 3 to 4 hours. 
2. Only found in reply chain bodies - The contact may have only been found in the body of a reply chain and no emails directly to or from the contact may have been found. While SigParser can extract email signature and other contact details for the contact it can't reliably say who the contact knows.
3. No one emailed the contact or received an email from the contact - If the contact was on an email chain and no one from your company responded to the email chain and the contact didn't send anyone at your company an email then no one has a relationship that could be detected thru emails. 
4. The contact BCC'd someone at your company - If the contact sent someone at your company a BCC email then those BCC'd emails will be ignored.

Over time as SigParser processes more emails it may find additional communication that will allow it to fill in these fields.