Http POST requests reach server more than once
<p>I develop a web application. 
Client side - Javascript/Typescript + AngularJS
Server side - c# - asp.net web api 2
IIS Express as host.</p>

<p>I noticed a wierd issue occuring in which POST requets reach the server more than once. For example, one scenario in which requests are sent multiple times, each request for a specific folder email is sent 3 times. I also see those request sent three times in the Network tab.</p>

<pre><code>public class mailsService extends ImailsService{

    static instance : ImailsService;

    // Dictionary of folder -&gt; emails
    public Folders;


    public mailsService(){
        var scope = this;
        myInterval = setInterval(function(){
                    // Making this request until getting a successful response - waiting for server to go up
            scope.webService.get("url to get my own place").success(data =&gt; {
                scope.myLocation = data;
                scope.isLocationInit = true;
                getAllMails();
                window.cleanInterval(myInterval);
            })
        }, 3000);
    }

    // This function happen on it's own when running the client code.
    // The service is a singleton therefore this code runs only once.
    public getAllMails() {
    if (!this.isLocationInit)
        return;
    var scope = this;
    scope.webService.get("url to get all folders").then(reponse =&gt; {
        var folders = response.data;

        for (var i = 1; i &lt;= folders.length; i ++){
                return scope.get("url to get the mails inside specific folder").then(initMails.bind(null, i));
        }});
    }

    public initMails (folderId : number, response){
        mailsService.instance.Folders[folderId].push(response.data);
    }
}

public class webService extends IwebService {
    public get(url : string){
        return this.$http.get(url);
    }

    public post(url : string, data : any){
        return this.$http.post(url, data);
    }
}


// Server side:

// Cross-Origin requests
[EnableCors(origins: "*", headers: "*", methods: "*")]
public class MailsController : ApiController 
{
    private IMailsService _mailsService;

    public MailsController(IMailsService service)
    {
        this._mailsService = service;
    }

    public IHttpActionResult GetAllFolders()
    {
        var result = _mailsService.GetAllFolders();
        if (result == null)
            return BadRequest("...");

        return Ok(result);
    }

    public IHttpActionResult GetFolderEmails(int folderId)
    {
        var result = _mailsService.GetFolderEmails(folderId);
        if (result == null)
            return BadRequest("...");

        return Ok(result);
    }
}
</code></pre>

<p>The controller fitting method hits twice or even more, although it is called only once from the cliend side code.</p>

<p>Is this something configurably? IIS wierd thing? I seriously don't know where to start looking.</p>