From V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016) :
UBE
Unsolicited Bulk Email (spam, Internet, UCE)
From The Jargon File (version 4.4.7, 29 Dec 2003) :
UBE
//, n.
[abbrev., Unsolicited Bulk Email] A widespread, more formal term for email
spam. Compare UCE. The UBE term recognizes that spam is uttered by
nonprofit and advocacy groups whose motives are not commercial.