3CX SMTP server - which IPs

[pacpac]

Hi, I am setting up my Exchange server to allow incoming mails from certain IPs. It looks like the mails are not coming from the static IP (which I have whittelisted) on the 3CX server since mails are blocked. I am using 3CX SMTP server. Does anyone know which IPs I shall whitelist on the Exchange server so mails are coming in OK? Thanks

 

[Saqqara]

Check post '10, mentions dns smtp-proxy.3cx.net https://www.3cx.com/community/threads/3cx-smtp-server-what-is-the-dns-and-ip-address.63414/

This maybe the incoming servers, but worth a try

 

[pacpac]

Hi, 'smtp-proxy.3cx.net' resolves to five IPs, tried to whitelist them all, no luck....

 

[StefanW]

sorry to ask, but why you allow incoming IPs to an exchange? only if the exchange shall relay mails (exchange is configured in PBX to send mails via your exchange) you must control the "from", inbound is general from "public". The IPs in the list are not the once which eventually send the mails... they are just our proxies to accept your mails if you use our cloud service...

 

[pacpac]

Sure, the Exchange server sits behind a spam filter on a separate server. Exchange is now only accepting mails from the spam filter server IP. However, I would like to have mails from 3CX coming in directly to Exchange thus bypassing the spam filter since sometimes there is a delay on this server. I am running a Freepbx instance as backup and have whitelisted the IP on that server, mails are coming in instant, would also like that from 3CX. Hope that gives some background.

I should add, this is Exchange 2016 and allowed IPs are set on the Receive Connector (scoping).