When using Donorfy's Web Widgets to collect donations online via either Stripe or GoCardless, you can set up the process to send the acknowledgments automatically so you do not need to manually action the sending of the email - see this article for details on how to set this up.
For GoCardless Web Widgets, there is also the option of using your own Direct Debit confirmation acknowledgments, which allows you to control the brand message so you are not reliant on GoCardless' standard emails and will result in fewer payment notifications being sent out to your supporters also - an added bonus! - see this article about how to turn the feature on and create your notifications.
An example custom GoCardless Notifications of this can be found here.
You may also want to add bits of data automatically, such as last donation amount, into the acknowledgment - you can find all of the available placeholders here: Acknowldgement Placeholders