difficulties to send mails

[vincentd401]

Hi,
I am working with SugarCRM 4.5.1e. The email setup if fine for the inbound emails with POP3, the test setting button give me a good answer and I receive mails in the box.
Then I am able to send mails as notifications for Meetings or Calls, those mails are using SMTP.
Then I can't send mails directly from the emails module (Compose Email). This seems to use PHPMailler with the Sendmail programm. I've tried to setup emails options with both external email client and sugar client. I also tried to change manually the PHPmailller class to set the Mailler as SMTP instead of Sendmail.
Nothing is working.
I don't have any errors when I send mails, but it take few minutes to send it. And I never receive any mails.
Any Idea?

[vincentd401]

Do somebody have any clues?
Please!
I'm stuck!