V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

UCE
       Unsolicited Commercial E-mail (Usenet, spam, UBE)


The Jargon File (version 4.4.7, 29 Dec 2003):

UCE
 n.

    [abbrev., Unsolicited Commercial Email] A widespread, more formal term for
    email spam. Compare UBE, which may be superseding it.