A customer told me that when they went to open an invoice I sent them they got a security warning that the SSL certificate was only for sendgrid.net ???

Hi there,

I want to make sure you get the support you need. It's vital your customer is able to view the invoice without any issues. From here I recommend contacting our support team using this link here. One of our agents will be happy to set you in the right path. 

Feel free to ask other questions. I'm here to assist.