Pseudo code

Parse mailing list

seek enf of file to get the size

define Find message:
if (size of file - current offset) is smaller than size of "From:",
memcopy the last (size of file - current offset) characters at the beginning of the buffer and load 
(size of buffer - ((size of file - current offset)) into the buffer

Look at the (current offset + lenght of "From:" - 1)th character in the buffer, if it is :, check previous, if it is m, check previous, etc...
If not, check if 

def boyer-moore(str, substr):
  lstr - len(str)
  lsubstr = len(substr)
  current = lsubstr - 1
  # As long as our current offset is within the string
  while (current < lstr):
    # Read the substring backward
    offset = 0
    while (str[current - offset] == substr[lsubstr - offset] and offset <= lsubstr): ++offset;
    if (offset == lsubstr and str[current - offset] == substr[lsubstr - offset]):
      # found match
      return current - offset
    if (offset < lsubstr):
      failing_char_index = lsubstr - offset
      # Didn't found a match, see if a letter in the substring match the failing letter in the string
      --offset
      while (str[current - offset] != substr[failing_char_index] and offset <= lsubstr): --offset
      if str[current - offset] == substr[failing_char_index]:
        # If we found a matching letter in the substring that matches the failing character
        # Shift the pattern to match those two together