Issue field - Email
Watch for changes
Issue field
Issue fields may be used to define steps in the approval process. For example, you may choose the approver to be the assignee or the reporter of an issue. You can use custom fields that are populated with your information.
External User
You can specify external users, outside your organization (without access to Jira) to participate in the approval process. We will send an email with an invitation to an external user in case of first interaction. They will have to setup an account. An external user can setup an account beforehand by visiting https://app.approval-path.com/register.html.
Once an account is setup and the email address is confirmed, they can log in to the dashboard and see a list of awaiting approvals.
Issue field - mail
Combing both above mentioned possibilities, issue field - Email allows you to specify external user steps that are more dynamic.
They field can be populated after the definition is created and started
You can select a list of external approvers (multiple external approvers)
You can Resolve user/s on approval start or step start. More here.

Issue field has to be accessible on create screen
You can use the “Short text (plain text only)” custom field for adding single email address fields to your tickets.

For multiple external approvers, you can use the description of an issue. This option is available as “Description” under the “Issue field - Email” dropdown menu.
In order for the description step to work, you must create a table with “Approval Path” header. Any email addresses inside the table are then assigned to an approval step. Here is a template:
Approval Path |
---|
Resolve user/users on
There are two options that allow you to reveal the approvers (value),
Approval start
Step start
If the “approval start” option is selected, the value will be revealed as soon as the the approval starts (in the event of the value missing from the issue field, this step will be skipped or definition will not be created when it doesn’t contain any steps).
Step start option, however, will only reveal the value once the path has reached to the step.