Receiving route; format is "regular expression@domain" or a specific email address. Required. Constraints: 1-128 characters (42007 when over length); must contain '@' (42007 when absent); the whole string must be a compilable regular expression (42007 otherwise); the suffix after the last '@' must be a non-blank domain (42003) that exists under the account (42004) and is available — domain status must not be 0, and when action is an email address the domain must also have MX verified (42005).

Target URL or email address. Required. Constraints: 1-255 characters (42009 when over length); must be either an http(s) URL matching the source URL pattern (host/port/path rules) or a valid email address (42009 otherwise). When action is an email address, apiUserRoute is required (42010); when action is a URL, apiUserRoute is ignored (stored as null).

Required when action is set to an email address; must be an existing API_USER under the account (42011 otherwise). Ignored when action is a URL.