Updating SMTP credentials for website

Hi

I have been asked to change the SMTP creadentials for web server. We host our servers on AWS and I will recreate the SMTP credentials in aws. My understanding is that I will update following setting in web.config file.

    <mailSettings>
      <smtp deliveryMethod="method" from="email address">
        <network host="weuseamazon" port="pno"  password="Iwillput passwordhere" userName="username" />
      </smtp>
    </mailSettings>

On the server under sites , I can see 4 subsites and all of them have web.config file which means I will have to update all those files.

Do I need to make any changes to IIS manager. Website is hosted on server 2012.

Thanks