for a promotion event, the 30 day timer doesnt start until you log in with a toon that meets the requirements (or in this case, account).
if you fail to meet the promotion requirements during the time of the promotion, you lose, the items will never appear in the mail.
*may have slightly misunderstood the question, i thought the items never appeared in the mail until your account met the requirements (ie active sub). disregard the above.
since its a question of being able to check the mail, to receive the items, that should be something for a "veteran account" concept. but doubt it works like that.