You can check with Sage to see if you need to use the 3-letter country codes or if the 2-letter ones are fine for your system. Publix Passport

Zip Codes now include country code as part of the primary key.  A zip code needs the system record, in the address' country code, for it to be accepted by Sage 100.  Using 3 digit codes allows you to benefit from the Sage provided USA zip code list (and the Canada list of postal codes, if you chose to install them).

2-Digit country codes work in Sage 100, but a mix just makes things more confusing.  We generally recommend using 3-digit country codes (updating existing addresses, and removing the 2 digit country codes), to benefit from the Sage lists, but the choice is yours.

We go with the three digit country code but UPS requires a two character code.  To resolve, we created a two character UDF in the SO header (populated via a script) and map the two character code to the UPS interface

After recent changes, you don't need a script for that anymore.  Just flow the UDF value from the system table's 2 digit code (AlternateCountryCode).

Even better!

good morning, i didn't realize that it's possible to install the Canada list of postal codes! Thanks for the tip.

Yes, it is in the server install program, after the modules list, after the demo companies list.  No space in the middle of the postal codes, which is a bit unconventional, but you get used to it.