On Premise Exchange 2019- Issue sending to external addresses

[DoohickyMicky]

This is my first on-premise Exchange setup since back in 2008SBS, so please forgive my ignorance...lots has changed.

My 2019 Exchange setup is being created for around five users in a small office, so we'd like to keep things simple.  No smart connectors.  Simple direct connection to ISP via firewall.  Not worried about receiving mail from external sources for the time being.

External Domain name:  example.com hosted on a standard webhost which hosts our website
Internal/local Domain Name:  whatever.example.com

I'd like the mail to show as coming from example.com.

My internal e-mail all works fine. 

However, when I send to external addresses, the e-mail is blocked as Junk by the external SMTP server (my ISP's server) because the outgoing mail comes from my internal server/domain (whatever.example.com) - which of course doesn't exist externally, so it is marked as SPAM by the ISP. 

Yet, when I run the testconnectivity (Outbound SMTP) tool, it passes with a warning about an SPF record (which, of course, doesn't exist for whatever.example.com).

I'm sure I'm missing something simple, but my searches have come up empty so far.

Any direction would be appreciated.

In the old SBS editions, a person could simply enter the SMTP FQDN of the ISP and external SMTP worked...that's sort of what I'm hoping to emulate.

Thanks!

[#2]

Sorry, it's a little bit confusing what your are describing. Are you saying that when a user emails externally, their email address suffix is @whatever.example.com and this is causing it to be tagged as spam?

[#3]

Just change the primarysmtpaddress of the user to your external domain.

[#4]

Hi @DoohickyMicky,

The easiest way would be to add the example.com domain as an accepted domain to your Exchange Server. After adding it as an accepted domain, you can change the default email address policy to make the example.com domain the primary domain and apply the policy to everyone (Email address policies in Exchange Server | Microsoft Learn) After you applied the new settings, everyone will have a Primary Email address of email address removed for privacy reasons. 

If your send connector is scoped to only whatever.example.com, you should add example.com as well. If your send connector is not scoped, you should be fine and your email will be send to your ISP.

To make sure that it's not marked as Junk, you should add an SPF record with the external ip address of your mail server to the public DNS of example.com.

I hope this helps.

Regards,

Ruud