Many users are complaining that my website takes too long to send the verification email after registering. And many users don't even receive the emails. Could you tell me what could be the possible problem?

HI, Gaurav.

Thank you for contacting us.
All emails that are sent by your site are processed by Joomla! All components that are built in into your site and are able to send emails are using - in a fact - using Joomla! processor. Joomla! may send emails in two ways:

- using phpmailer server script
- or SMTP

First you should check what method do you use to send emails in Backend -> System -> Global configuration -> Server -> Mail settings

Then you will know where possible fault could be: if you're using php mailer, then in your server, if SMTP then in your SMTP email server.

So if you are using php mailer then change it to SMTP... if you're using SMTP already, try to use other email server (e.g Google).

Please, note that this issue is rather not related with JomSocial and we could not help you a lot in this issue.