Dividend investing is a tried-and-true strategy for generating strong, steady returns in economies both good and bad. But as Corporate America's slew of dividend cuts and suspensions over the past few years has demonstrated, it's not enough simply to buy a high yield. You also need to make sure those payouts are sustainable.

Let's examine how Windstream (NYSE: WIN) stacks up in four critical areas to determine whether it's a dividend dynamo or a disaster in the making.

1. Yield
First and foremost, dividend investors like a large forward yield. But if a yield gets too high, it may reflect investors' doubts about the payout's sustainability. If investors had confidence in the stock, they'd be buying it, driving up the share price and shrinking the yield.

Windstream yields a whopping 8.9%, considerably higher than the S&P's 2.2%.

2. Payout ratio
The payout ratio might be the most important metric for judging dividend sustainability. It compares the amount of money a company paid out in dividends last year with the earnings it generated. A ratio that's too high -- say, greater than 80% of earnings -- indicates that the company may be stretching to make payouts it can't afford, even when its dividend yield doesn't seem particularly high.

Windstream has an enormous payout ratio of 192%. But, like many telcos, it generates considerably more free cash flow than net income. On a free cash flow basis, its payout ratio declines to a much-more-reasonable 77%.

3. Balance sheet
The best dividend payers have the financial fortitude to fund growth and respond to whatever the economy and competitors throw at them. The interest coverage ratio indicates whether a company is having trouble meeting its interest payments -- any ratio less than 5 is a warning sign. Meanwhile, the debt-to-equity ratio is a good measure of a company's total debt burden.

Let's examine how Windstream stacks up next to its peers.

Company

Debt-to-Equity Ratio

Interest Coverage

Windstream 908% 2 times
CenturyLink (NYSE: CTL) 101% 3 times
Frontier (NYSE: FTR) 172% 2 times
Verizon (NYSE: VZ) 63% 9 times

Source: S&P Capital IQ.

It's not unusual for telcos to carry lots of debt, though Windstream appears to carry a heavier burden than most of its peers.

4. Growth
A large dividend is nice; a large growing dividend is even better. To support a growing dividend, we also want to see earnings growth.

Over the past five years, earnings per share have declined at an annual rate of 13%, while its dividend has grown at a 37% rate, though some of that decline is due to one-time charges, and things don't look so bad on a cash-flow basis.

The Foolish bottom line
Windstream exhibits a somewhat mixed dividend bill of health. It has a massive yield and a high but reasonable free cash flow payout ratio. But regardless of whether a cut is imminent, dividend investors will want to keep an eye on the company's significant debt load. To stay up to speed on Windstream's progress, add it to your stock watchlist. If you don't have one yet, you can create a free, personalized watchlist of your favorite stocks.