NTT DoCoMo Inc. said Friday the trial service of its next-generation mobile phone service launched Wednesday experienced e-mail server problems from 6 p.m. Thursday until 12:30 p.m. Friday.

The 4,500 people who received the mobile phones on a free-rental basis, mainly in Tokyo and Yokohama, were unable to receive e-mail because of trouble with a device that determines whether e-mail is to be sent to the next-generation phones or ordinary cellular phones.

The glitch also affected 23 million subscribers of DoCoMo's current i-mode service.

The service promises electronic data transmission at between 64 kilobits per second and 384 kbps -- six to 40 times faster than current service.

DoCoMo hopes to launch the service commercially Oct. 1, initially limiting its coverage to a 30-km radius from the center of Tokyo. Current plans call for the service to be extended to Osaka and Nagoya in December and to other cities next spring.