It really depends on your mission and from where you intend to drive revenues.
Asking a guest to create an account and log in in order to send an email to your customers could be seen as a stumbling block.
The more you can encourage visitors to reach out to your customers, the more your customers will have a great experience,
On the other hand, you have to make sure you all the security measures in place so your customers do not get spammed through your site.
Give me a call to discuss further. I offer a free initial call to first time clients. Use this link:
Good things : 1. It may lead to revenue generation and make you active to get jobs and business without any restrictions.
Bad things: 1. Some times users become fade up by getting unwanted calls and email notifications.
Conclusive Points: I think everything should be in restrictive way so clients should be happy on marketplace websites.
You may check my marketplace