Update third_party-exchange_onprem.md

docs/third_party-exchange_onprem.md

@@ -16,7 +16,7 @@ This setup becomes very handy if you have enabled the [Office 365 security defau
 Your mailcow needs to relay all mails to your personalized Exchange Host. It is the same host address we already looked up for the mx Record.
 
 1. Add the domain to your mailcow
-2. [Add your personalized Exchange Host address as relayhost](/firststeps-relayhost)
+2. [Add your personalized Exchange Host address as relayhost](/u_e-postfix-relayhost)
 3. Add your personalized Exchange Host address as forwarding host to unconditionally accepted all relayed mails from Exchange. (Admin > Configuration & Details > Configuration Dropdown > Forwarding Hosts)
 4. Go to the domain settings and select the newly added host on the `Sender-dependent transports` dropdown. Enable relaying by ticking the `Relay this domain`, `Relay all recipients` and the `Relay non-existing mailboxes only.` checkboxes
 
@@ -39,4 +39,4 @@ The easiest way to validate the hybrid setup is by sending a mail from the inter
 - Mails sent from the mailcow to a mailbox in the internet cannot be sent. Non Delivery Report with error `550 5.7.64 TenantAttribution; Relay Access Denied`  
 **Possible Solution:** The authentication method failed. Make sure the certificate subject matches an accepted domain in Exchange. Try authenticating by static ip instead.
 
-Microsoft Guide for the connector setup and additional requirements: https://docs.microsoft.com/exchange/mail-flow-best-practices/use-connectors-to-configure-mail-flow/set-up-connectors-to-route-mail#prerequisites-for-your-on-premises-email-environment
+Microsoft Guide for the connector setup and additional requirements: https://docs.microsoft.com/exchange/mail-flow-best-practices/use-connectors-to-configure-mail-flow/set-up-connectors-to-route-mail#prerequisites-for-your-on-premises-email-environment