The unacknowledged life of 'exceptioned' and 'unexceptioned'
Both exceptioned and unexceptioned appear often enough in Google Books search results to yield Ngram graphs. Here is the Ngram chart for the period 1800–2008 for exceptioned (blue line) and unexceptioned (red line):
As the chart indicates, unexceptioned is the earlier word. A Google Books search finds matches for it dating back to Daniel Defoe, "The Parallel: or Persecution of Protestants the shortest way to prevent the Growth of Popery in Ireland" in A Second Volume of the Writings of the Author of The True-born Englishman (1705):
And as no testimony of the good Deeds of a Person, or a Party, can come with such unexceptioned Authority as what has the concurring Testimony of their Enemies, we refer the Reader for the Particulars; to the famous Milton, whose Pen must needs obtain Credit of our high Gentlemen since he Quarrels with the very Men they would quarrel with, and falls in with the fury of the Times, to expose those they would have exposed.
Unexceptioned seems to be have been used almost exclusively as an adjective during its three centuries of existence. The meaning appears to be "without exception, or not admitting of exceptions." I was surprised to find that the Compact Edition OED of 1971 has no entry for unexceptioned, considering that the word goes back so far in English literature, and that a Google Books search finds about 150 unique matches for the term overall, including several from 2014.
'Exceptioned' as an adjective
The earliest match for exceptioned in Google Books search results involves its use as an adjective, too. From a letter of James Bowdoin to Thomas Pownall (December 3, 1770), reprinted in The Bowdoin and Temple Papers, volume 1 (1897):
As soon as it was known by one of sd messages that they [the proposed bills] would not [be assented to with certain words in them], the House striking out the exceptioned words im[m]ediately sent ye sd bills to ye Council, who passed them.
Here exceptioned appears to mean "taken exception to, or criticized." But more-recent instances of exceptioned as an adjective seem to carry the meaning "excepted, or exceptional," as in Frederick Bruner, The Churchbook: Matthew 13–28 (2004):
Where there is no repentance, Jesus' exception means that some divorces are the (“exceptional” or “exceptioned”) will of God. Here Moses and Jesus agree. Where divorce is the exceptioned will of God, Jesus protects such divorced persons from the opprobrium that is sometimes cruelly attached to them, as though all divorced persons are, as such, less than God's best persons (because, it is said, all divorce is less than God's best will).
The same general sense of exceptioned as an adjective appears in tech publications such as G. Neufeld & M. Ito, Protocols for High Speed Networks IV (2013):
Cells belonging to other connections can be processed once the exception condition is saved (even if these connections share the same endpoint as an exceptioned connection). We cannot process cells belonging to the exceptioned connection, even if they are not affected by the exception, since some applications may depend on the per-channel ordering guarantee of ATM cells.
'Exceptioned' as a verb
Exceptioned first appears in Google Books search results as a verb in Francis Spilsbury, Free Thoughts on Quacks and their Medicines, Occasioned by the Death of Dr. Goldsmith and Mr. Scawen (1776):
Indeed by such railings against every ingredient which is made use of, were we to exclude, one after another, from the several medical compositions, all those which might now and then be exceptioned, we would soon find ourselves reduced to return to that time of ignorance, when disorders were deemed incurable.
Here again, exceptioned seems to mean "taken exception to"—but this time as a past-tense verb, rather than as an adjective. But more recent usage shows the term being used to mean "treated as an exception [to some rule]." For example, from Steve Hughes, Jim Samuelson & S. Miller, SQL Server DTS (2002):
Overflows that actually occur during transformation cause the row to be exceptioned. You can specify this value when the source values are all (or mostly) within the range of the destination column. In total Google Books finds more than 170 unique matches for exceptioned without regard to whether the word is being used as an adjective or as a verb.
I suspect that exceptioned feels right to the poster because in the field of IT in which he works the term is part of the nomenclature—whether technical, colloquial, jargony, or otherwise. Under the circumstances, the question "Is it a word?" seems fairly easy to answer affirmatively—especially since it has been around for more than 240 years in other senses.
The crucial question is whether the people that the poster is trying to communicate with will recognize the intended sense—and the rightness—of the word (as he does) or will be baffled by it. If the poster feels reasonable confident that the intended audience will understand the word, I see no reason to avoid using it, either as an adjective or as a verb.