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I saw no indication that vBulletin support this functionality, in fact some indication it does not:
http://www.vbulletin.com/forum/showthread.php?300725-Mailing-List-integration
Again there are some hints that this can be added yourself:
http://www.vbulletin.org/forum/showthread.php?t=151222&highlight=mailing+list
Integration with common identity stores.
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