Do you already have the same coffer of accessories in your inventory? If you've been through the post Stormblood MSQ since the launch of Shadowbringers, you might have received it as a quest reward. The coffers are unique items so you wouldn't be able to retrieve the one in the mail until you open the other one or place it on a retainer.

Try removing the boost item from the mail separately instead of using Take All so you can at least use it and get the job boosted.