mail is probably the most common used function with the worst set of error reporting available to it

mail() returns true on success and false on error, but this "false" is all you can get with php, when as you have to examine the mailer logs to see if the message acctually failed (i for example get false on the mail() function, but the email is queued and sent with sendmail)

there should be atleast somekind of trigger_error() sequence which would spew out a few E_NOTICE or E_WARNING triggers depending on the progress of mail() - for example.. if the sendmail_path directive isn't configured properly, some incorrect data (any of the parameters beeing null, empty or not set), or you cant connect to the mail server (windows - only guessing that it doesnt report that), or whatever kind of message the mailer spews out resulting in true/false

any kind of verbosity, even if only trough E_NOTICE or E_WARNING would really be appreciated, a simple true or false is just not enough when tracking down why mail() returns false.