It's a very low-level problem, just trying to figure out

The problem is very low, just want to understand, please advise
Why does PHP mail automatically send e-mails, e-mail not all to stmp the server's account number and password?
Mail (to,subject,message,headers,parameters), why this can be sent, is not every computer installed STMP service Ah, a little confused

------Solution--------------------
Who says not to configure it?

[Mail Function]
; For Win32 only.
; Http://php.net/smtp
SMTP = localhost
; Http://php.net/smtp-port
Smtp_port = 25

; For Win32 only.
; Http://php.net/sendmail-from
; sendmail_from = [email protected]

; For Unix only. Supply arguments as well (default: "Sendmail-t-i").
; Http://php.net/sendmail-path
; Sendmail_path =

; Force the addition of the specified parameters to be passed as extra parameters
; to the SendMail binary. These parameters would always replace the value of
; The 5th parameter to mail (), even in safe mode.
; mail.force_extra_parameters =

; ADD X-php-originating-script:that would include UID of the Script followed by the filename
Mail.add_x_header = On

; The path to a log file, the would log all mail () calls. Log entries include
; The full path of the script, line number, to address and headers.
; Mail.log =
------Solution--------------------
You can look at PHP. INI in the related configuration
------Solution--------------------
It means that Apecha has been configured.
------Solution--------------------
There's one!
------Solution--------------------
discuss

Who says not to configure it?

[Mail Function]
; For Win32 only.
; Http://php.net/smtp
SMTP = localhost
; Http://php.net/smtp-port
Smtp_port = 25

; For Win32 only.
; Http://php.net/sendmail-from
; Sendmail_fro.

------Solution--------------------
This is the server well-equipped ...
------Solution--------------------
The cute LZ
------Solution--------------------
If you send e-mail with SendMail, the native configuration is OK, you do not need SMTP
But it's so big, it's easy to be considered spam rejection.
------Solution--------------------
Account password port Service mailbox to set something else.

------Solution--------------------
In fact, it can also be set in the PHP program. For example, you use QQ e-mail. Can go to QQ mailbox to open the SMTP service

