Google's Gmail Web-based email service runs on the Internet Message Access Protocol system, but it also offers Post Office Protocol mail server access.
Definition of LUMEN. 1. 2. : the bore of a tube (as of a hollow needle or catheter). 3. : a unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of one candle intensity.
In biology, a lumen (from Latin lÅ«men, meaning an opening; plural lumina) is the inside space of a tubular structure, such as an artery or intestine.By extension, the term lumen is also used to describe the inside space of a cellular component or structure, such as the endoplasmic reticulum.n biology, a lumen (from Latin lÅ«men, meaning an opening; plural lumina) is the inside space of a tubular structure, such as an artery or intestine.