The Use of -STOP-

Most senders are confused when they use verb "stop" to convey the meaning of quitting activity/something to receiver. They frequently place "to" to split out the verb subsequent to "stop". If they, in general, want to mean "Don't do anything", the form must be:

stop + noun/gerund [meaning : stop something/doing something]

Example : The students must know that smoking can cause lung cancer. So, they should stop smoking anyway.
Meaning : .... stop smoking ..... [Students won't smoke.]

But, someone keep saying "Please stop to smoke". If they address this kind of sentence to ask someone not to smoke, the meaning is contradicted. "Please stop to smoke" means "please stop what you are doing in order to smoke" or "please smoke by quitting what you are doing". So, don't put "to" after "stop" when you want to ask someone not to do something. You can put "to" after "stop" if you want to ask someone to stop something in order to do something.

In summary, "stop" can convey two sets of meaning with "to" and without "to". With "to" means "Take an action" while without "to" means "Don't take an action".

Example 1 [with "to"]

The orders given by customer are very low now, you should stop to solve this issue.
Meaning = The orders given by customer are very low now, you should solve this issue by quitting other activity. Or, the orders given by customer are very low now, you should stop other activity to solve the issue.

Example 2 [without "to"]

The customers comment our junk mail sent to them, please stop sending irrelevant messages to them.
Meaning = The customers comment our junk mail sent to them, please don't send irrelevant messages to them.