MailPoet and Spam

Hi,
I’m trying to properly set up my newsletter on my WP.

I have created an alias email using my domain name on my tutanota email provider (something like: [email protected]).

And then I set up this email address to be used by MailPoet and Woocommerce.

Everything seems to be working fine, except I keep receiving spam emails on my gmail address (in the main box, not in the spam folder), seemingly coming from my [email protected] address, but sent by “m1.sendingservice.net” which looks a lot like a MailPoet CNAME record I had to add to my DNS to set up MailPoet.

I don’t know how spam is being sent form my [email protected] and I don’t know why my gmail address is receiving the spam (it’s listed in my WooCommerce Client list, so that might be a clue).

Maybe I took this backwards and should not have started by creating the email alias?

I am not sure if this is all very clear, but if someone has a clue as to where the problem is coming from, that would be very helpful.
(I am managing to use wordpress by reading tutorials and such, but I am no developper ((and I am French so sorry if my english is awkward)).