FOR TAX YEAR 2018 AND PRIOR

It depends.  It can be. In order to be treated as alimony, your divorce or separation agreement cannot stipulate that it is not alimony.  It must also meet the criteria below.  If it meets the criteria to be considered alimony and is not in a category specifically listed as Payments Not Alimony, then yes, you would be able to take the alimony paid deduction. 

"A payment is alimony only if all the following requirements are met:

• The spouses don't file a joint return with each other;
• The payment is in cash (including checks or money orders);
• The payment is to or for a spouse or a former spouse made under a divorce or separation instrument;
• The divorce or separation instrument doesn't designate the payment as not alimony;
• The spouses aren't members of the same household when the payment is made (This requirement applies only if the spouses are legally separated under a decree of divorce or of separate maintenance.);
• There's no liability to make the payment (in cash or property) after the death of the recipient spouse; and
• The payment isn't treated as child support or a property settlement."

Payments Not Alimony

Not all payments under a divorce or separation instrument are alimony. Alimony doesn't include:

• Child support,
• Noncash property settlements, whether in a lump-sum or installments,
• Payments that are your spouse's part of community property income,
• Payments to keep up the payer's property,
• Use of the payer's property, or
• Voluntary payments (that is, payments not required by a divorce or separation instrument).

https://www.irs.gov/taxtopics/tc452