What are the IP addresses of Gmail?

Google is using SPF. That means google say “all gmail(dot)com come from these IP-addresses; everything else is fake”

Submit this command in a cmd-window:

1. c:\> nslookup -type=txt _spf.google.com 
2. Server: google-public-dns-a.google.com 
3. Address: 8.8.8.8 
4.  
5. Non-authoritative answer: 
6. _spf.google.com text = 
7.  
8. "v=spf1 include:_netblocks.google.com include:_netblocks2.google.com include:_netblocks3.google.com ~all" 

Then you can look up the includes:

1. C:\>nslookup -type=txt _netblocks.google.com 
2. Server: google-public-dns-a.google.com 
3. Address: 8.8.8.8 
4.  
5. Non-authoritative answer: 
6. _netblocks.google.com text = 
7.  
8. "v=spf1 ip4:64.233.160.0/19 ip4:66.102.0.0/20 ip4:66.249.80.0/20 ip4:72.14.192.0/18 ip4:74.125.0.0/16 ip4:108.177.8.0/21 ip4:173.194.0.0/16 ip4:209.85.128.0/17 ip4:216.58.192.0/19 ip4:216.239.32.0/19 ~all" 
9.  
10. C:\>nslookup -type=txt _netblocks2.google.com 
11. Server: google-public-dns-a.google.com 
12. Address: 8.8.8.8 
13.  
14. Non-authoritative answer: 
15. _netblocks2.google.com text = 
16.  
17. "v=spf1 ip6:2001:4860:4000::/36 ip6:2404:6800:4000::/36 ip6:2607:f8b0:4000::/36 ip6:2800:3f0:4000::/36 ip6:2a00:1450:4000::/36 ip6:2c0f:fb50:4000::/36 ~all" 
18.  
19. C:\>nslookup -type=txt _netblocks3.google.com 
20. Server: google-public-dns-a.google.com 
21. Address: 8.8.8.8 
22.  
23. Non-authoritative answer: 
24. _netblocks3.google.com text = 
25.  
26. "v=spf1 ip4:172.217.0.0/19 ip4:172.217.32.0/20 ip4:172.217.128.0/19 ip4:172.217.160.0/20 ip4:172.217.192.0/19 ip4:108.177.96.0/19 ~all" 
27.  
28. C:\> 

This is all the IP-addresses google is sending from. These are not depending on where you are or what device you are using, because they are owned by google and nobody else can use them.

Addresses sent to:

1. C:\>nslookup -type=mx google.com 
2. Server: google-public-dns-a.google.com 
3. Address: 8.8.8.8 
4.  
5. Non-authoritative answer: 
6. google.com MX preference = 20, mail exchanger = alt1.aspmx.l.google.com 
7. google.com MX preference = 10, mail exchanger = aspmx.l.google.com 
8. google.com MX preference = 30, mail exchanger = alt2.aspmx.l.google.com 
9. google.com MX preference = 50, mail exchanger = alt4.aspmx.l.google.com 
10. google.com MX preference = 40, mail exchanger = alt3.aspmx.l.google.com 

Looking these up from France:

1. C:\>nslookup aspmx.l.google.com 
2. Server: google-public-dns-a.google.com 
3. Address: 8.8.8.8 
4.  
5. Non-authoritative answer: 
6. Name: aspmx.l.google.com 
7. Addresses: 2a00:1450:4013:c00::1b 
8. 108.177.119.26 
9.  
10.  
11. C:\>nslookup alt1.aspmx.l.google.com 
12. Server: google-public-dns-a.google.com 
13. Address: 8.8.8.8 
14.  
15. Non-authoritative answer: 
16. Name: alt1.aspmx.l.google.com 
17. Addresses: 2404:6800:4008:c04::1a 
18. 74.125.204.27 
19.  
20.  
21. C:\>nslookup alt2.aspmx.l.google.com 
22. Server: google-public-dns-a.google.com 
23. Address: 8.8.8.8 
24.  
25. Non-authoritative answer: 
26. Name: alt2.aspmx.l.google.com 
27. Addresses: 2607:f8b0:400e:c04::1b 
28. 74.125.28.26 
29.  
30.  
31. C:\>nslookup alt3.aspmx.l.google.com 
32. Server: google-public-dns-a.google.com 
33. Address: 8.8.8.8 
34.  
35. Non-authoritative answer: 
36. Name: alt3.aspmx.l.google.com 
37. Addresses: 2607:f8b0:4003:c06::1b 
38. 64.233.160.26 
39.  
40.  
41. C:\>nslookup alt4.aspmx.l.google.com 
42. Server: google-public-dns-a.google.com 
43. Address: 8.8.8.8 
44.  
45. Non-authoritative answer: 
46. Name: alt4.aspmx.l.google.com 
47. Addresses: 2607:f8b0:4001:c19::1b 
48. 108.177.121.27 

From Denmark:

1. C:\>nslookup aspmx.l.google.com 8.8.8.8 
2. Server: google-public-dns-a.google.com 
3. Address: 8.8.8.8 
4.  
5. Non-authoritative answer: 
6. Name: aspmx.l.google.com 
7. Addresses: 2a00:1450:4010:c07::1b 
8. 173.194.73.27 
9.  
10.  
11. C:\>nslookup alt1.aspmx.l.google.com 8.8.8.8 
12. Server: google-public-dns-a.google.com 
13. Address: 8.8.8.8 
14.  
15. Non-authoritative answer: 
16. Name: alt1.aspmx.l.google.com 
17. Addresses: 2607:f8b0:400e:c04::1a 
18. 74.125.28.27 
19.  
20.  
21. C:\>nslookup alt2.aspmx.l.google.com 8.8.8.8 
22. Server: google-public-dns-a.google.com 
23. Address: 8.8.8.8 
24.  
25. Non-authoritative answer: 
26. Name: alt2.aspmx.l.google.com 
27. Addresses: 2607:f8b0:4003:c06::1b 
28. 64.233.160.26 
29.  
30.  
31. C:\>nslookup alt3.aspmx.l.google.com 8.8.8.8 
32. Server: google-public-dns-a.google.com 
33. Address: 8.8.8.8 
34.  
35. Non-authoritative answer: 
36. Name: alt3.aspmx.l.google.com 
37. Addresses: 2607:f8b0:4001:c19::1b 
38. 108.177.121.27 
39.  
40.  
41. C:\>nslookup alt4.aspmx.l.google.com 8.8.8.8 
42. Server: google-public-dns-a.google.com 
43. Address: 8.8.8.8 
44.  
45. Non-authoritative answer: 
46. Name: alt4.aspmx.l.google.com 
47. Addresses: 2607:f8b0:4002:c03::1b 
48. 173.194.219.27 

The addresses changes, could be depending on time and/or location, so if you want to do firewalling, you have to automatically build up a list of acceptable IP’s dynamically.