How to Suggest a Feature or Improvement for iPhone Mail

"The electrical pulses (...) have varied pulse widths because of the operation of PWM, and their actual pulse widths depend on the associated sinusoidal duty cycle function."
Pulse and sine function apply to laptop status LEDs. Their description is from U.S. patent 6,658,577: Apple have a monopoly on making status lights look as if they breathe.
Their breathing status LED indicator is not only new, of course, it is also improved — or, as Apple put it, "better and more improved".
Now, do you have an idea for a better and more improved iPhone Mail?
›› Who knows best what iPhone Mail lacks? You, of course! Here's how to let Apple know about what's missing from iPhone Mail, what should work differently — and what doesn't work for you.