command line - Why can't I connect to Google's SMTP server on port 25?

I'm working on an InfoSec exercise, specifically email spoofing. I started by executing the following commands:

C:\Users\student>nslookup
6.0.0.10.in-addr.arpa
        primary name server = localhost
        responsible mail addr = nobody.invalid
        serial  = 1
        refresh = 600 (10 mins)
        retry   = 1200 (20 mins)
        expire  = 604800 (7 days)
        default TTL = 10800 (3 hours)
Default Server:  UnKnown
Address:  10.0.0.6

> set type=mx
> gmail.com     //the name of the mail domain of the victim
Server:  UnKnown
Address:  10.0.0.6

Non-authoritative answer:
gmail.com       MX preference = 20, mail exchanger = alt2.gmail-smtp-in.l.google
.com
gmail.com       MX preference = 10, mail exchanger = alt1.gmail-smtp-in.l.google
.com
gmail.com       MX preference = 40, mail exchanger = alt4.gmail-smtp-in.l.google
.com
gmail.com       MX preference = 5, mail exchanger = gmail-smtp-in.l.google.com
gmail.com       MX preference = 30, mail exchanger = alt3.gmail-smtp-in.l.google
.com
> exit

After these initial commands have been executed, I'm now gonna accessed telnet:

C:\Users\student>telnet alt1.gmail-smtp-in.l.google 25
Connecting To alt1.gmail-smtp-in.l.google...Could not open connection to the host,
on port 25: Connect failed

Can someone please tell me why I can't connect to port 25? Thanks!

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