Return unique records based on shared column in 2 tables
Assuming Account is on CustList, the following example should get you going:

--Set up demo data
SET NOCOUNT ON

DECLARE @Visits TABLE (Id INT,Account INT,DateOfVisit DATE,TimeOfVisit TIME)
DECLARE @CustList TABLE (Id INT,Account INT,EmailAddress VARCHAR(100))

INSERT INTO @Visits (Id,Account,DateOfVisit,TimeOfVisit)
VALUES (1,1,'2017-05-25','08:00:00')
INSERT INTO @Visits (Id,Account,DateOfVisit,TimeOfVisit)
VALUES (1,1,'2017-05-25','10:00:00')

INSERT INTO @Custlist (Id,Account,EmailAddress)
VALUES (1,1,'MyEmail@Test.com');

--Common Table Expression for distince account numbers
WITH DistinctAccountsVisits
AS (
    SELECT DISTINCT Account
    FROM @visits
    WHERE TimeOfVisit IS NOT NULL
        AND DateOfVisit = '2017-05-25'
    )
--Join Visits with CustList on Account
SELECT v.Account
    ,c.EmailAddress
FROM DistinctAccountsvisits v
JOIN @CustList c ON c.Account = v.Account