How is sendmail sending emails without port 25 opened? [closed]

I have Amazon AWS server which I'm configuring to receive emails.

AWS states that port 25 is closed for outgoing connections unless you specifically apply to have it opened.

But I tried to send an email anyway with sendmail from the command prompt, and it was delivered successfully.

How did this happen?

Solution 1:

SMTP only needs port 25 for incoming connections. To send a mail any local port can be used in conjunction with port 25 on the remote mail server.