Countries without postcodes (updated from https://gist.github.com/kennwilson/3902548 )

COUNTRIES_WITHOUT_POSTCODES_2018.rb

COUNTRIES_WITHOUT_POSTCODES = [
    [ "Angola", "AO" ],
    [ "Antigua and Barbuda", "AG" ],
    [ "Aruba", "AW" ],
    [ "Bahamas", "BS" ],
    [ "Belize", "BZ" ],
    [ "Benin", "BJ" ],
    [ "Bolivia", "BO" ],
    [ "Botswana", "BW" ],
    [ "Burkina Faso", "BF" ],
    [ "Burundi", "BI" ],
    [ "Cameroon", "CM" ],
    [ "Central African Republic", "CF" ],
    [ "Chad", "TD" ],
    [ "Comoros", "KM" ],
    [ "Congo", "CG" ],
    [ "Congo, Democratic Republic of the", "CD" ],
    [ "Cook Islands", "CK" ],
    [ "Cote d'Ivoire", "CI" ],
    [ "Curaçao", "CW" ],
    [ "Djibouti", "DJ" ],
    [ "Dominica", "DM" ],
    [ "Equatorial Guinea", "GQ" ],
    [ "East Timor", "TL" ],    
    [ "Eritrea", "ER" ],
    [ "Fiji", "FJ" ],
    [ "French Southern Territories", "TF" ],
    [ "Gabon", "GA" ],
    [ "Gambia", "GM" ],
    [ "Grenada", "GD" ],
    [ "Guyana", "GY" ],
    [ "Heard and McDonald Islands", "HM" ],
    [ "Hong Kong", "HK" ],
    [ "Kiribati", "KI" ],
    [ "Macao", "MO" ],
    [ "Mali", "ML" ],
    [ "Mauritania", "MR" ],
    [ "Nauru", "NR" ],
    [ "Netherlands Antilles", "AN" ],
    [ "Niue", "NU" ],
    [ "North Korea", "KP" ],
    [ "Qatar", "QA" ],
    [ "Rwanda", "RW" ],
    [ "Sao Tome and Principe", "ST" ],
    [ "Seychelles", "SC" ],
    [ "Sierra Leone", "SL" ],
    [ "Solomon Islands", "SB" ],
    [ "South Sudan", "SS" ],
    [ "Suriname", "SR" ],
    [ "Syria", "SY" ],
    [ "Tokelau", "TK" ],
    [ "Togo", "TG" ],	
    [ "Tonga", "TO" ],
    [ "Tuvalu", "TV" ],
    [ "Uganda", "UG" ],
    [ "United Arab Emirates", "AE" ],
    [ "Vanuatu", "VU" ],
    [ "Yemen", "YE" ],
    [ "Zimbabwe", "ZW" ]
]

Looks good. You might want to add UK as a duplicate of GB.

GB is the correct ISO code, but UK is the country it represents (Great Britain is an island, and not equivalent to UK. For instance, Northern Ireland is in the UK but not in Great Britain)

Nicaragua and UAE do not use postal codes officially. I can confirm from our own operations as a company and staff we have out there.

@MaxShineOn Updated

Changes based on https://en.wikipedia.org/wiki/List_of_postal_codes

Removed:

• Ireland "IE"
• Malawi "MW"
• Mauritius "MU"
• Montserrat "MS"
• Panama "PA"
• Saint Kitts and Nevis "KN"
• Saint Lucia "LC"
• Somalia "SO"
• South Africa "ZA"
• Tanzania, United Republic of "TZ"
• Timor-Leste "TL"
• Trinidad and Tobago "TT"

Added:

• Gabon
• Bolivia
• Chad
• Curaçao
• East Timor
• Heard and McDonald Islands
• South Sudan
• Togo