First time Install and Config Exchange Server 2019: Some questions

[jamesn450]

Hello everyone,

I am pretty new to Exchange Server 2019 so I decide to give it a try from installation to final config

I have processed the following:

1/ Register public domain (testexchange.com and mail.testexchange.com for example), setting up A record and MX record, pointing to our public IP: All good, using mxtoolbox.com show DNS record publised and all.

2/ Install Exchange Server 2019 on Windows Server 2019 - Standard edition: All latest updates done

3/ Config Accepted Domain, Send and Receive connector

4/ Create 2 mail receipients so far: Administrator and User1

5/ Sending and Replying a Test mail between the Administrator and User1 successfully

6/ From outside of LAN, I can access OWA and ECP, check email via web-page browser successfully

But so far, I cannot send nor receive any outside (Internet) email... I tried to send a test email from User1 to a google mail or other public emails, it said there is a delayed, with error message for example as per the following:

"Server at gmail.com (142.250.152.27) returned '451 4.4.397 Error communicating with target host. -> 421 4.2.1 Unable to connect -> SocketTimedout: Socket error code 10060'

Am I missing some steps along the above?

Thank you again for your patience and support

Kind regards

[#2]

While reading https://www.frankysweb.de/community/exchange2019/451-4-4-397-error-communicating-with-target-host/ it could be an issue on Google's side. Have you tried to send to a gmail.com domain? Or have you tried port 2525?

[#3]

OK, so I learn that my ISP has blocked the port SMTP 25 which is used by most mail server to send/receive mail from/to outside mailer. I have asked the ISP to release the port however, they said it's blocked by the spam policy and not an option to open it, unless it's a registered commercial IP
What are the option that I have in this scenario? Using different port or anyway to bypass the port 25?
Thank you

[#4]

You can't bypass it. You have to have the port free, the other thing you can do is to use a smart host service. Have you pointed you MX records to your Firewall? Do you have any send connectors configured?
https://docs.microsoft.com/en-us/exchange/plan-and-deploy/post-installation-tasks/configure-mail-flo...