Yes. As long as the bishopric received the envelope before the end of the year (or it was mailed before the end of the year) you can create a batch to deposit it for 2016. Start a batch in MLS like normal. The first thing it asks is for the date of the batch. Normally you leave that date alone but in this case change the date to Dec 31, 2016. Then enter the donation in that batch and process the batch like normal. Do not enter anything in the batch except donations received or mailed before the end of the year. If needed, you can then do another normal batch for any other donations you may have that belong in 2017.