One in every four I-mode customers comes from a rival German operator, claimed chief executive officer Uwe Bergheim, and the company has also attracted more than 100 content service providers, he said.
E-Plus hopes to increase average revenue per customer, presently hovering around €22 (£14) per month for standard GSM services, by 20% through I-mode.
NTT DoCoMo in Japan developed the technology, which allows users to send and fetch e-mail and receive other Internet services. The Tokyo mobile operator has, meanwhile, attracted around 33 million customers with the technology.
I-mode is being closely monitored by third-generation mobile operators in Europe planning advanced data services, such as high-speed Internet access and video, over their broadband networks. If I-mode takes off, its popularity would be a big boost for 3G.