I have a Nokia e90, callers can't hear me but I can, why is that?

SOURCE: Nokia E90 Communicator - callers can hear me but I cannot hear

Not certain... but you need to check menu - tools - settings - general - enhancement and make sure your default is set to "headset".
When you plug headphones only (not the headset/mic combo) into the 2.5mm jack, it will go into a headphone mode where you can hear through the headphones but you must speak through the phone microphone - it sounds like it is going into that mode on you. It can only be the setting above or possible a short in the jack (though that doesn't really explain why it is happening only when you receive a call).
If you have 2.5mm headsets (or can pick up a small 3.5 to 2.5 adapter), you can also try having them call you and see if you can hear through the headphones - that would prove it is going into headphone only mode.

SOURCE: Nokia E90 Communicator - callers can hear me but I cannot hear

try to format your phone, and check if thhe problem persists.
FOR SOFT-RESET:

- at Standby Screen type-in => *#7780#
It will ask for “Restore all phone settings-phone’ll restart….”
Then it asks for security code enter factory default => 12345


FOR HARD-RESET:

- at Standby Screen type-in => *#7370#
It will ask for “Restore all phone settings-phone’ll restart….”
Then it asks for security code enter factory default => 12345


FOR FLASHING- TOTAL RESTORE: (Do this if your phone does not boot up)

1) Remove the battery, and then wait for about 20 min or so before putting it back

2) Press and hold these three keys together -Green dial key, Star key[*], Three key [3]

3) switch ON the phone.

4) Do not let go the three keys until you see the WELCOME screen displayed and just let it complete the boot process.

check if this helps. if this doesnt help contact Nokia Care Point-> http://europe.nokia.com/A4388379
thanks for using FixYa