Mail App Cannot send mail issue

I have been using my Mac for about 4 months now. I configured the Mail App with my email account, and I used it daily.

There is one problem i encountered since the begining, one which i cannot explain.

If i launch the app and try to send an email, everything works just fine. But if I leave the app open for a long time (hours), i get the "Cannot send mail" alert when i try to send a message:

.

The email I just tried to send is nowhere to be found. But if i just quit the app and relaunch it, the outbox folder appears for a few moments, and my email is sent immediately.

At first, when the problem occurred, I just kept composing new mails and tried to send them, but to no avail. As a result, when i finally quit the app and relaunched it, all those emails were immediately sent...


Anybody else had this problem? What exactly is going on in there? Is the connection to the SMTP server timing out? The server does not support IDLE? Are there any settings that need to be tweaked?

Thanks.

Welcome to Mac-Forums

This is strange since you are not maintaining a connection to the POP/IMAP/SMTP services while Mail is running. The connections are made when needed and terminated once the necessary actions are complete.

As a test, can you install another Mail program like Thunderbird or something and see if it has the same issue?

What version of OS X are running BTW

Problem occured on both Lion and Mountain Lion