Company offered incentive but refused to pay. To sue or not to sue?

My company offered me an incentive through email last month but now the company refused to pay. My questions:

1. Is the offer via email binding?
2. What options do I have?

Why ask a question whereby you only can answer.

Sue and you will lose your job... that's all.....

No - if you sue and lose your job because of the lawsuit. You can have another claim in unfair dismissal. 

Now - back to your question. 
1. Offer through e-mail is binding provided some contractual criteria are fulfilled. I need to have a look at the e-mail and your conduct thereafter. 

2. Options you have is to (1) discuss with your employer (2) put subtle pressure such as engaging a lawyer etc. Sometimes, things can be settled out of court as well. 

I have similar question on incentive/commission payment. In the case, I have gotten a deal/PO from the customer and we invoice immediately and payment is 30 days.

In the case, if I leave the company, will I still be able to claim commission since I got the PO in? Or do I have to wait for payment to be made by customer before I tender in my resignation?

The content of this thread is focused on the following :

Commissions offered as an incentive for Sales & Marketing Personnel

My personal perspective as both ex-employee as well as ex-employer.

1.  Every thingy is dependent on what is stated in the Employment Contract /Agreement and is being signed on by both parties.

2.  There are many forms of incentive commissions offered, personal sales, group sales, quarterly group sales qualifier, commissions to be paid when (after collections).

3.  Normally commissions are not paid together with monthly wages, this is done to bypass employment laws.

4.  In essence, incentives is not wages and can be withdrawn anytime by the company. Incentives commissions /bonuses can be based on personal KPI or on Group /Team total KPIs.

5.  If there is a serious breach of the T&C of an employment contract, the legal recourse for wages dispute is taken up by Labor Court or IRC. For breach of contract, it is often referred to the Civil Courts. IRC is mainly for "Reinstatement" and if in the event of too long a period has lapsed, the Court could order a compensational amount.

6.  For "Constructive Dismissal", a case can be more successful in Civil Courts (personal opinion) and the compensation can be higher. But legal fees can eat up any awards.

As for part of the Q asked as above :

Or do I have to wait for payment to be made by customer before I tender in my resignation
My personal opinion is to wait for the commissions paid out first before resigning.

When a person resigns, a lot of things, events can happen beyond control and can be out of jurisdiction of courts. This is my personal experiences in LC / IRC as an independent observer (non-legal).