I tried to send a mail but it comes on screen that no URLs is allowed in mail or subject. I do not understand what I have done mistake.
Hi Yasin,
URL stands for Universal Resource Locator. In simpler words, it is the address of the site. www.Zameen.com, www.Google.com are examples of URLs.
The error you encountered means that you cannot put a URL or a website's address neither in the email nor its subject. Try removing all of the URLs you have inserted in the text of the email and its subject and see if it goes through.