Mailing effectively isn't just about the address or the list. Knowing what's going on in the country is necessary, too, particularly for marketing mailings. Natural disasters, elections, and holidays all distract our potential customers. Some of these are known well in advance and can be built into a marketing calendar. And while a disaster can't be predicted, more knowledge will let you decide whether to hold a mailing for a short while.
There are advantages available with more information, too. For example, some holidays associated with gift giving might provide a new opportunity for catalogers who plan sufficient lead time. Holiday greetings can be another way to communicate with your clients – and let them know you are aware of their culture. As with New Year's greetings for January 1, some expressions of good wishes are neutral in some cultures.
Basic news has become easy to access online. For a more local perspective, try Newspapers.com with over 10,000 newspapers from around the world. With this many links, some are broken but there are plenty of choices in most countries. (Since many of these papers are not in English, I recommend "translate" on Google's tool bar for a quick look at the basics.)
Holidays make a difference, too. Mailing to Japanese consumers during the week of holidays in the Spring will mean lower and delayed response, as will mailing to Moslem consumers during Ramadan. There are many others: Chinese New Year is widely celebrated in East Asia and in Chinese communities worldwide and the Indian Festival of Lights (variously called Deepavali, Depawali, Dipavali, Dewali, Diwali, Divali, Dipotsavi, or Dipapratipad) is celebrated in India and in Hindu communities in other countries.
Many sites provide holiday information. Here are a few that I use. OANDA, in addition to its currency conversion calculator, has holidays around the world searchable by country. Infoplease has a list of major holidays, holidays in some world religions, and national days. Many of the web sites for U.S. Embassies list the major holidays in the country where the embassy is located, most often under "About Us".
And don't forget that it is now Spring in the Southern Hemisphere. While I am thinking about new Winter boots, it's time to buy Summer clothes and bathing suits and picnic supplies and camping goods there. Almost everyone who lives near the equator buys clothes and gear for hot weather year 'round, with some exceptions for higher altitudes.
Plan ahead and enjoy finding out more about our world while you improve your mailing's effectiveness.