But we don't have a sendgrid account and can't control how this connector uses sendgrid?
We are using this connector and it is rewriting our <a> tags to sendgrid addresses:

Unfortunately we can't use the standard mail connector which uses 365 as we only have on-prem mailboxes, but we are pushing to get a 365 box just to use the connector.
I have had to go through every single one of our flows and remove "https://" from every link - which wasn't a quick task.