Sure, here you go:

CREATE TABLE Request

(

RequestId INT NOT NULL,

EmailAddress VARCHAR(50) NOT NULL

);

CREATE TABLE Quote

(

QuoteId INT NOT NULL,

RequestId INT NOT NULL,

CreatedAt DATETIME NOT NULL

);

INSERT INTO Request VALUES (1, 'joe@bloggs.com');

INSERT INTO Request VALUES (2, 'bob@bloggs.com');

INSERT INTO Quote VALUES (1,1,'2012-09-04 14:00');

INSERT INTO Quote VALUES (2,1,'2012-09-04 14:30');

INSERT INTO Quote VALUES (3,1,'2012-09-05 12:51');

INSERT INTO Quote VALUES (4,1,'2012-11-09 09:00');

INSERT INTO Quote VALUES (5,1,'2012-11-09 11:00');

INSERT INTO Quote VALUES (6,2,'2012-09-04 15:00');

INSERT INTO Quote VALUES (7,2,'2012-09-04 15:00');

INSERT INTO Quote VALUES (8,2,'2012-12-30 19:30');

INSERT INTO Quote VALUES (9,2,'2012-12-30 19:30');

SELECT

r.RequestId

,q.QuoteId

,r.EmailAddress

,q.CreatedAt

,CASE

WHEN DATEDIFF(dd,LAG(q.CreatedAt,1) OVER (PARTITION BY r.EmailAddress ORDER BY q.CreatedAt),q.CreatedAt) > 30

THEN 1

ELSE 0

END AS GroupResetFlag

,DENSE_RANK() OVER(PARTITION BY r.EmailAddress ORDER BY q.CreatedAt) AS InitialRank

FROM

Request r

INNER JOIN Quote q

ON r.RequestId = q.RequestId

ORDER BY

r.EmailAddress

,q.CreatedAt;

I've included a slightly modified query to use the created tables.