IPs for SMTP connection whitelisting - Google SMTP rejecting IO SMTP connections

Nick S. shared this question ago

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Google SMTP is rejecting HELO from Inflatable Office, so I would like to try whitelisting them via our Google Workspace settings. The error itself is attached as well. It's not giving an authentication error or anything of that nature, only a generic -1, which is why I'd like to switch from SMTP Authentication to IP based whitelisting.

I do not see Inflatable Office's IP ranges listed for SMTP connections, though I did find some Wordpress related IP addresses.

208.64.38.12

209.250.2.66

209.250.2.70

Are these also the addresses from which Inflatable Office connects to 3rd party SMTP services such as smtp-relay.gmail.com?

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Joel A. ● 18 days ago

you'd want to whitelist these two IPs:

208.92.218.149

209.250.2.66

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Nick S. ● 18 days ago

Awesome - Is there a way to bypass the InflatableOffice request for a username/password?

I've configured our SMTP relay to work off whitelisted IPs for any address in our domain without requiring authentication, but I'm unable to send a test message from InflatableOffice without including a password.

Edit: To clarify - Previously, I would use SMTP authentication and I would use an "App Password" but Google depreciated those and now requires OAuth. So my only option for SMTP relay is via IP whitelisting and not SMTP authentication.

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Joel A. ● 17 days ago

I'm fairly certain google still supports app passwords. You'd need to have 2-step verification on though. you'd have to reach out to google for more info.

https://support.google.com/accounts/answer/185833?hl=en

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Nick S. ● 17 days ago

That was the issue, I just got off a support call with Google over the same thing. They discontinued "Less secure apps" but App Passwords are still fine with 2SV.

I thought we had 2SV enabled on the main account because it prompts for a code, but it's technically disabled. Fixing that now and we should be good.

I'll still whitelist the IPs in addition just for the extra security. Thanks for the assistance, that's what I get for assuming and not verifying.

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