I still thing you could apply some rules as detailed by me here ...
Yes, some of those rules are fine, but requires a lot of dev. Although it's a hack, a trigger can be done in several minutes.
E.g. posting my code again
CREATE TABLE [dbo].[SpamPhrase](
[Id] [int] IDENTITY(1,1) NOT NULL,
Phrase [nvarchar](50) NOT NULL,
PRIMARY KEY CLUSTERED
CREATE TRIGGER QueuedEmailSpamBlocker
SET NOCOUNT ON
if exists ( select 1
from inserted i
join SpamPhrase s on i.Body like '%'+s.Phrase+'%'
where i.Subject like '%Contact us%'
insert into [SpamPhrase](Phrase) values ('some spammy phrase')