In order to allow emails to be sent from your domain, we must set up an SPF (Sender Policy Framework) record mechanism giving Mandrill--the emailing service AskNicely uses--permission to send emails under your domain name. All requirements are prescribed by Mandrill.
As a Global Standard, a Domain can only contain up to 10 mechanisms in its SPF record; exceeding this limit means that there will not be enough room to add the required Mandrill mechanism.
Option 1: Deleting Pre-Existing SPF Records
The most straightforward option is to delete some of the pre-existing SPF mechanisms within the SPF record (such that there are 9 or less). The SPF txt record can be found within your domain's DNS records. Click Here to access a tool that can be used to count and visualize SPF mechanisms.
It is important to note that some of the mechanisms might be important to pre-existing emailing systems. You should contact your Email Administrator for assistance.
Option 2: Create a new subdomain
Another option is to create a new subdomain and using that subdomain to send emails instead. The SPF record on this domain will be empty and thus not exceed the 10 mechanism limit. This method requires more technical know-how and should be done by the Email Administrator or Support.
Option 3: "Flatten" your SPF mechanisms
Finally another option is to modify your SPF records through a method known as 'SPF Flattening', which reduces the number of SPF mechanisms. Additional information regarding this can be found here. The article has a 'SPF Record Flattener' at the bottom of the page showing examples of this.
Please note for any of the options above: SPF/DNS changes can take up to 24 hours to apply (depending on the provider).
Once you have a domain with an acceptable SPF record, you can resubmit it in 'Step 1' of your Settings > General > Email Domain page, then proceed to 'Step 2' of the email domain setup process.