See the below thread. Seems their way of 'fixing' something is just to delete everything

https://quickbooks.intuit.com/learn-support/en-uk/other-questions/re-the-have-a-great-day-signature/...

The thought process behind all of this is what is doing my head in. Simple things like the missing logos off pruchase orders and statments is another bug bear of mine. They can't even fix simple things like that, so not holding out much hope they have the talent of the ability to fix this email issue.