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 AT&T (NYSE: T) 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.

AT&T yields 5.7% -- certainly worthy of further investigation.

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.

AT&T's payout ratio is 48%. On a free cash flow basis, the payout ratio is 70%.

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.

AT&T's debt-to-equity ratio is 58%. Its interest coverage rate is 6 times.

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.

Let's examine how AT&T stacks up next to its peers.

Company

5-Year Annual Earnings-Per-Share Growth

5-Year Annual Dividend Growth

AT&T 18% 4%
Verizon (NYSE: VZ) (9%) 4%
Sprint Nextel (NYSE: S) N/A* N/A
MetroPCS (NYSE: PCS) 10% N/A

Source: Capital IQ, a division of Standard & Poor's. * Negative earnings.

Of domestic peers focused on the wireless market, Verizon's dividend is most comparable. Neither Sprint nor MetroPCS pays dividends currently.

The Foolish bottom line
AT&T exhibits a fairly clean dividend bill of health. It has a reasonable payout ratio, moderate leverage, and high earnings growth.

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Ilan Moscovitz doesn't own shares of any companies mentioned. You can follow him on Twitter at @TMFDada. Motley Fool newsletter services have recommended buying shares of AT&T. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.