[verbovet]

A sieve script can be used instead of the green check mark. For example:

if
  allof(
  address :is "From" "noreply+calendar-reminder@fastmail.com",
  header :contains "X-Spam-known-sender" "yes",
  header :matches "From" "*"
  )
{
  set "fromwas" "${1}";
  deleteheader "From";
  addheader "From" "☛ ${fromwas}";
}