javax.mail.Message#getAllRecipients() returns null in case no To: or Cc: header exists in the message (which happens when an email is sent using only a Bcc: field).

Likewise, javax.mail.Message#getFrom() can return null if there is no From: header (I don't know of a valid reason for that).

Such emails should not imported when filtering on recipient or sender respectively, since there is no recipient/sender to check.

We currently don't treat that, resulting in a dumb NullPointerException