> I recently switched from Eudora to the Mac Mail which came with OS X.5
>
> Mac Mail worked well but all of a sudden it won't send. Any solutions?
>
> In the meantime I have gone back to Eudora.
I can think of two problems I've run into which generate the same
symptoms: (1) somehow, the default account for sending got switched
or modified in someway, so that it is no longer valid; (2) Mail
encountered an error when trying to send mail (perhaps a transient
connectivity glitch) and so is still in "off-line" mode.
Check for (1) by looking in the Mail Preferences, and confirming
that all settings (including any port numbers and/or passwords)
are correct.
Check for (2) by looking for a little Alert symbol - this would
appear beside the Inbox item in the mailbox pane on the left.
If Mail got stuck sending, you will also see an Out box (I forget
exactly how it is labelled). If you see the alert symbol,
double-click on it...