Mails are not seding from mass contact form

Hi all,

I have a strange problem. I have created a mass contact category for all editors and I have 2 editors.When I send mail from mass contact form to editor's category, it displays a successful message that mail sent to 2 users : email1, email2.
But I am not getting any emails.
I have installed mime mail module and mails are sending using SMTP.
One another problem is that sometimes my mass_contact menu disappearing from navigation and when I manually hit url (www.example.com/mass_contact) then it shows that "Page not found".
then I have to disable/enable module and it comes then.

Any help is much appreciated.