Just got this email, seems to be targeted.
T&C's do state that it's available on your "second online shop". I've only ever done one online order so you might have to be in the same boat.
Anyway, check your emails just in case!
T&C':
$20 off your order offer
~To claim your $20 off your order you must spend $100 or more (excluding bag fees) at www.woolworths.com.au in a single transaction, select Pick Up or Delivery and enter promo code DMY20 at checkout. Offer valid once per shopper on their second online order only between Monday 5th October and Sunday 11th October inclusive. Offer can only be redeemed by the recipient of the email containing this offer. Minimum spend amount excludes any vouchers or offers, delivery charges and Delivery Saver items, tobacco/smoking products, gift cards, egift cards, mobile recharge, travel cards and tickets and Pre-order Kiosks and Auto-order products. Orders may be cancelled by us without notice to you if the above terms and conditions are not adhered to. Please note that to redeem your $20 off offer, your order total must be $100 or more after any other discounts or offers. Excludes the Woolworths PFD bulk ordering range.
I got $20 off $120 Online Order but may not use it as my previous purchases have been $54 or less. Hope to get a 4 week x $50 spend for 10,000 points deal. Have not used this account for 2 months.