beh le mail temporanee avranno un dominio del tipo @tempmail.it o @pjjkp.com... basta che recuperi la lista di questi domini e quando l'utente effettua la registrazione verifichi che non sia nella lista..

EDIT: dai sono buono e ti risparmio la fatica...

codice:
0815.ru
2prong.com
4warding.net
anonbox.net
beefmilk.com
bofthew.com
bugmenot.com
courrieltemporaire.com
dacoolest.com
despam.it
disposemail.com
dodgit.com
dontsendmespam.de
e4ward.com
emailmiser.com
fakeinbox.com
filzmail.com
get1mail.com
gishpuppy.com
guerrillamailblock.com
hochsitze.com
ieatspam.eu
incognitomail.com
jetable.com
junk1e.com
litedrop.com
m4ilweb.info
mail4trash.com
mailexpire.com
mailinator.net
mailme.lv
mailzilla.org
mierdamail.com
mypartyclip.de
no-spam.ws
nogmailspam.info
nospam4.us
nowmymail.com
pjjkp.com
prtnx.com
regbypass.com
safetymail.info
selfdestructingmail.com
slopsbox.com
sofort-mail.de
spamavert.com
spambog.com
spambox.info
spamcero.com
spamfree24.de
spamfree24.net
spamherelots.com
spaminator.de
spaml.de
spamspot.com
suremail.info
tempe-mail.com
tempemail.net
tempmail.it
temporaryinbox.com
thisisnotmyrealemail.com
trash-amil.com
trash2009.com
trashmail.net
trashymail.net
webm4il.info
whyspam.me
yopmail.com
0clickemail.com
3d-painting.com
4warding.org
anonymbox.com
binkmail.com
brefmail.com
bumpymail.com
curryworld.de
dandikmail.com
discardmail.com
dispostable.com
dodgit.org
dump-email.info
email60.com
emailtemporario.com.br
fakeinformation.com
fizmail.com
getonemail.com
great-host.in
h.mintemail.com
hotpop.com
ieatspam.info
incognitomail.net
jetable.net
kulturbetrieb.info
lookugly.com
mail-temporaire.fr
mailcatch.com
mailin8r.com
mailinator2.com
mailnator.com
mbx.cc
mintemail.com
myphantomemail.com
nobulk.com
nomail2me.com
nospamfor.us
onewaymail.com
politikerclub.de
quickinbox.com
s0ny.net
sandelf.de
shitmail.me
smellfear.com
sogetthis.com
spambob.net
spambog.de
spambox.irishspringrealty.com
spamday.com
spamfree24.eu
spamfree24.org
spamhole.com
spamkill.info
spammotel.com
spamthis.co.uk
teewars.org
tempemail.biz
tempinbox.co.uk
tempomail.fr
thanksnospam.info
throwawayemailaddress.com
trash-mail.com
trashmail.at
trashmailer.com
tyldd.com
wegwerfemail.de
willselfdestruct.com
yuurok.com
10minutemail.com
4warding.com
amilegit.com
antispam.de
bio-muesli.net
bsnow.net
cosmorph.com
cust.in
deadaddress.com
discardmail.de
dodgeit.com
dontreg.com
dumpyemail.com
emailinfive.com
emailwarden.com
fastacura.com
fr33mail.info
getonemail.net
guerillamail.com
haltospam.com
hulapla.de
imails.info
ipoo.org
jetable.org
lhsdv.com
lopl.co.cc
mail.by
maileater.com
mailinator.com
mailme.ir
mailnull.com
meltmail.com
mt2009.com
mytrashmail.com
noclickemail.com
nomorespamemails.com
nospamthanks.info
owlpic.com
pookmail.com
recode.me
safe-mail.net
saynotospams.com
skeefmail.com
snakemail.com
spam.la
spambob.org
spambog.ru
spambox.us
spamfree24.com
spamfree24.info
spamgourmet.com
spamify.com
spaml.com
spamobox.com
supermailer.jp
tempalias.com
tempemail.com
tempinbox.com
temporaryemail.net
thankyou2010.com
tmailinator.com
trash-mail.de
trashmail.com
trashymail.com
uggsrock.com
wh4f.org
wuzupmail.net