Is "mom" a proper noun when it refers to multiple individual mothers?

Having read When should "Mom" and "Dad" be capitalized?, I am confused about what feels like an edge case to me. Context:

A client wants to send out an email to multiple customers, with the subject, "A special day for mom." Given that "mom" in this case is referring to each recipient's mother, this seems like the "specific reference" case, so the correct sentence should be "A special day for Mom." But at the same time, "Mom" is referring to a different individual for each reader, hence my feeling of ambiguity.

Thanks for any confirmation/clarification!

Solution 1:

If I'm correct that this is a marketing question, my answer (as a 20+ year copywriter/creative director) would be to capitalize "mom," since most everyone reading the email has or has had a specific, nameable mother of one sort or another. If you can substitute a name for the word "mom," use a cap. Also - and this is the crucial bit for marketing/advertising verbage - go with what looks best.