Subscription – error confirmation email

Hello Mailpoet support team, and community,

I’m getting the following error message when I try to subscribe to our newsletter:

“There was an error when sending a confirmation email for your subscription. Please contact the website owner.”

And I’m getting the following error message when I try to manually resend a confirmation Email:

“There was a problem with your sending method. Please check if your sending method is properly configured.”

We are using the free version of Mailpoet (we have a little less then 300 subscribers).

We are using Mailpoet as sending method; we have an account and it was validated; our activation key is valid.

The same email address is configure for sending “from” and “reply-to”.

What could be the problem? How could I solve it?

I thank you in advance for your help.

The page I need help with: [log in to see the link]