cat pronz.txt | grep -i <value below> | wc -l

  @yahoo.:      11241
  @gmail.:      4176
  @hotmail.:    3976
  @aol.:        640
  @live.:       587
  @msn.:        147
  @mailinator.: 18
  
  1234:         1728
  pron:         215  # edit: -1 for the 2nd line
  password:     91

I have a vague feeling there's something to be learned here, but I'm not sure what it might be.