Subject text in emails

Hi -

Thanks so much for an awesome plug-in.

I am not collecting the user’s name when they subscribe to the newsletter. I’ve noticed all of the emails getting sent have a comma in them e.g. “Welcome aboard,” – I think that’s indicating that it’s looking for a name to insert there and leaving it blank. Where can I change the subject lines of emails so it just says “Welcome Aboard!” without the name value inserted?

Thanks so much!

Andy