Why is WOTIO sending duplicate account activation emails?

[AFDmenz]

Hello! 
I'm testing the process for sending out account activation emails using Wotio. 
I've set up the customer segment in Shopify and pushed the test through Wotio, everyone on the test list is receiving 2 emails (the same email twice). 

We thought this was happening because the sending email address wasn't verified, it now is and it's still happening. 

Has this happened to anyone else?
Tess