Hey, November and December are a big, important time period for online retailers. Lots of people always ask me what they should do to minimize the risk of deliverability problems during this period. Keeping in time that ISP email volumes are up (way up), ISP staff managing unblocking requests are probably getting more requests than usual, and that they all have holidays they're going to go on at some point. There's not always going to be a backup contact able to help. Responses are going to be slower. Maybe even less forgiving, out of frustration.
So what is the one most important thing you can do to make sure you don't have to deal with any of this? Avoid surprises. This isn't the time of the year to experiment. Don't add a new list. Don't buy a list. Don't mail a seven year old list that you just found in the back of a cabinet (that really happened). New lists, new data sources, anything you haven't been mailing to recently already, that adds new risk. Without knowing the reputation history of mailing to these "new to you" subscribers -- and how they're going to react to your mail in particular, you're opening yourself up to deliverability trouble.
Avoid that trouble. Don't start changing things now. Get through the season before adding more variables to what you're doing.