M1 have both cmda and gsm.
I got this from hotmid.com M1 spec sheet.
Network : GSM/GPRS/EDGE/WCDMA/HSDPA/HSUPA 900/1800/1900/; 850/2100MHz
And t-mobile 3G is on 1700 MHz/2100 MHz. I believe the 2100 Mhz should work for t-mobile. Am I understanding this wrong?