Hi Cameron,
I'm not the best person to answer this as I don't actually use the e-mail system in WeBWorK much. However, my bet is "no," there isn't a way within WeBWorK to automatically send an e-mail to a student who has just been added.
Similarly, I doubt that WeBWorK has the ability to filter users for e-mail by their completion of a given assignment.
Cheers,
Gavin
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Emails
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