You can set up your Web Widgets, Donation Forms or Campaign Donation Pages to automatically send an email when the donation is received - if you decide not automatically send the acknowledgement emails the emails will be queued up for you to send later - see Sending Acknowledgements in this article
To automatically send emails make sure that 'Send Acknowledgement Emails Immediately' is set to Yes on your Web Widgets, Donation Forms or Campaign Donation Page.
You can change this setting for existing Web Widgets, Donation Forms or Campaign Donation Page easily and you do not have to change any Form URLs or regenerate the Widget.
Below is an example of the setting in a Web Widget - the option is named the same for Donation forms and Campaign Donation Pages:
Record of Sent Acknowledgement
The details of the sent acknowledgement will be recorded within the Transaction header section - the Acknowledgement Name and the Date Acknowledged will be populated. This can be reported via a Transaction List also.
Problems sending the email
If there is a problem sending the email - e.g. your email server cannot be contacted, then the acknowledgement will be included in the list of outstanding acknowledgements - see Sending Acknowledgements in this article