Sending sms directed to port 5001, but few phones like nokia E series are receiving these smses at default port. All phone's default port is 0 then how these phones are receiving these smses.
If I recall correctly, on most (all?) Symbian devices, if an SMS is received on a port AND its character set is human-readable (i.e. its not a binary SMS, but is UCS2 or 7-bit text) AND there is no on-device client listening on that port, then it is inserted into the Inbox.
I think you will find that if you have a client on port 5001 which receives these messages, they won't end up in the Inbox.