As Bob mentioned the port for smtp is 25.
Port 25 is the original standard email SMTP port and the oldest, since it first debuted in 1982. Today, the Internet Assigned Numbers Authority (IANA), the group responsible for maintaining the internet addressing scheme, still recognizes port 25 as the standard, default SMTP port.
On the modern web, there’s not a single SMTP port. Instead, there are four common SMTP ports:
25
587
465
2525
If you’re configuring your WordPress site or email client to send emails via SMTP (submission), you’ll almost always want to use port 587. Again, this is the default SMTP port for submission and it supports secure transmission via TLS.
If port 587 is blocked for some reason, port 2525 is a common alternative. Again, this is not an officially recognized SMTP port, but it is commonly used and supported by most providers.
While many providers still do support port 465 for SMTP, it’s no longer an accepted standard and you should always try to use ports 587 and 2525 before using port 465.
Finally, while port 25 is commonly used for SMTP relay, you should not use it when setting up an email client or WordPress website because most ISPs and cloud hosting providers block port 25.
I left you this reference How to Choose the Right SMTP Port (Port 25, 587, 465, or 2525)
