Scott -
I had a mailing service for 19 years before I closed my business about a year ago.

Yes -  Access should be able to print the Postal Barcode no problems.  I used to merge from Word all the time in addition to the specialized machines I had.
You will need a special font - The fonts I have on my computer are USPS4CB and USPSIMBStandard.  Google those.

Be aware that the requirements are quite complex to create  a valid IMB Bar Code.  It's based on Address, Zip Code, Check Digits, and a number of other things to create the "string" that the barcode uses.
Not quiet as simple as the old PostNet bar code that used to be used.

Also do a search on the USPS website for IMB Barcode.  www.USPS.gov
This web site will give you a taste for what is needed in creating the IMB.

Wow. That's all new to me, Scott. I haven't done anything with postal barcodes since PostNet back in Word 2003, I think. LOL

The whole switch to the IMB is part of the reason I got out of the mailing biz.  They totally depreciated the Postnet bar code and it doesn't work by the way.
I had a special software that I had to run my addresses through to generate the correct files.  The cost on the software when I quit was at $3,000 a year just for the 90 day updates required by the PO.
That was before I even turned on the lights.  People just aren't mailing that much any more because of the high costs.  I can send an email practically for free.

Exactly. I don't even know why the post office still delivers mail 6 days a week. Drop it to once a week and they could save tons. Most correspondence is electronic nowadays. If you have something that NEEDS to get there in a day or two, there's FedEx and UPS. The only thing I get in the mail is JUNK. All of my bills are online. I almost never get actual written correspondence.