If you plan to contact lots of users (and sending lots of invitations), it is better to use a dedicated emailing service.
How many email invitations can you send?
A user can send up to 10 invitations per 24 hours period in your marketplace. If the "Users can only join this marketplace with an invite from another user" option is enabled in your Admin panel, this limit is increased to 50 invitations per day per user.
If an invitation is sent to multiple emails, each email sent counts for one invitation.
When should you use a dedicated emailing service?
If you plan on promoting your marketplace to dozens or hundreds of potential users, you should use a dedicated emailing service. Using a dedicated tool also has some benefits:
When emailing lots of people, it may be considered spam if not done properly. Being classified as spam can hurt your future marketplace email deliveries. A dedicated emailing tool offers some features that help you avoid this, such as better delivery time management or advanced anti-spam settings.
Dedicated services offer tools that give you more insight into metrics such as delivery, open rate, links clicked, and bounces.
You have more control over the sign-up link, meaning you can add some tracking parameters to it. Combined with Google Analytics, this lets you track how many people sign up from which channels.
With an emailing service, you can write the content you want and simply add a link to your marketplace homepage or to your marketplace sign-up page.
Can you use an emailing service if your marketplace is invite-only?
Unfortunately, at present, invitation codes (that are mandatory to create an account if your marketplace is invite-only) can only be generated with invitations sent from the marketplace.
You won't be able to use an emailing service in that situation as you can't generate and send an invitation code from your emailing service.
For that reason, the limit of invitations sent per day is set to 50 invitations per day per user.
What emailing services can you use?
There are lots of dedicated emailing services, many of them free to use as well. Here are some we can recommend: