What is the port 465 for Google SMTP?

For the gmail or what?

Use port 25 for SMTP or port 587 for ESMTP. The two different ports are to avoid sending an email from one address to another or sending the same email to a different email address. It's because each domain has an email server that can check the legitimacy of the email. For example, we cannot send an email to your @gmail.com email address to our @company.com address because each server only allows a single IP address to have access to their server.

Port 465 is used by both SSL and TLS. It is for use with Google's mail server. Using 465 will give you a secure session on their mail server (if they have one).

Using port 25 or 587 will allow you to connect to any mail server and use their smtp server, but it will be unencrypted and not as secure. If you use SSL or TLS, then they will automatically use 465 on their end. They will also tell you to use 465 if you try to use that port on a mail client.

Why is SMTP port 465 not working in Gmail?

I have the following problem.

I have SMTP enabled for my domain and I've set up my email forwarding through Google Apps (so my SMTP is on port 587). However when I try to send an email from my iPhone, Gmail says it cannot send because the server doesn't respond to SMTP on port 465. But when I check the connection attempts from my iPhone, it says the SMTP server replies to SMTP on port 587.

I can't see anything wrong with your configuration. Try to change the MX record for your domain and see if it works.

Also, if you are using Gmail in Android or iPad, they probably do not have full access to the server and just connect through their own mail servers.