I would like to customize the auto TY email that is generated to a donor once a donation is made. Can I do this? If so- can you please tell me how? Thanks so much!
There are a few places that contribute to the TY email.
On the Receipt tab of the Contribution page config you can add a message there in "Receipt Message".
Also any 'pay later' instructions will also be inserted.
The main template that sucks those bits in and adds a lot of other bits is under > Administer > Communications > Message Templates then click on System Workflow Messages and look for eg Contributions - Receipt (on-line)