Thold email send but a long time after

[Avenger]

Hi,
Frst I'm sorry for my english because I'm french...
Cacti 0.8.6j
Thold 0.3.1
PHP 5.1.6-pl6-gentoo

All my thold alerts are working and when I have an host down it's the same but I received the email a lot of time after( aproximatly 10 hours after ).
When I check my mailbox the time and the date of the email are those of the alert and not the time when I got the email.

So I would like to know if someone have any idea about where the problem can come from ( maybe it's on my php options).
Thx for the reply.