Outook client connectity from office network to office 365

Question

Hi All,

We have Exchange 2016 environment with us, In the firewall we have whitelisted the ports, URL's and ip address given under the topic Exchange Online present in the below link. We have also successfully executed the hybrid configuration wizard as well

I have gone through the below link, i don't see anything mentioned precisely for the below question. For your information, we are using Microsoft outlook 2016.

https://learn.microsoft.com/en-us/microsoft-365/enterprise/urls-and-ip-address-ranges?view=o365-worldwide

My question is, Before mailbox migration to office 365, I wanted to confirm the ports, URL's and ip address to be whitelisted in the firewall for outlook user in my office network to connect the mailbox migrated to office 365 ? Please help me with your inputs on this question.

Answer 1

@Nithyanandham Singaravadivelu

If you have opened all needed ports in that article, there shouldn't exist issue. Here also an article about ports for Exchange hybrid.

If you're still unsure about it, you could create a mailbox on Exchange online for testing. It is similar to migrated mailbox.

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

---

Answer 2

Hi KyleXu

Good Morning, Thank you for your response. I am able to create the remote mailbox and mailbox migration is also working fine. Also i can access the mailbox migrated to office 365 using outlook 2019 installed from my personal laptop connected to internet.

The problem is, The outlook 2016 version "16.0.4266.1001" used by customer from the laptop connected to domain/Lan network is not connecting to the mailbox migrated to office 365. At first, i have suggested customer to update the latest patches for outlook 2016, then asked them to outlook connectivity to office 365.

I know outlook 2016 latest version would use direct connect method to connect the mailbox in office 365, I wanted to understand the port and office 365 endpoints to be whitelisted specifically for outlook client to connect the mailbox in office 365 using the laptop connected to domain/Lan network ? if you could mention that details specifically, I would also ask their network team to cross check the given ports\endpoints are already whitelisted in their firewall.

Answer 3

Hi KyleXu, Hi All

Sorry, I think my question is not clear. Let me re phrase my question. Could anyone clarify me on this.

Is all the ports mentioned in the below link have to be opened in the proxy/firewall for outlook client to connect the mailbox in Exchange online ?

https://learn.microsoft.com/en-us/microsoft-365/enterprise/urls-and-ip-address-ranges?view=o365-worldwide

In that above link Microsoft 365 Common and Office Online - What are these ports used for ?

Answer 4

@Nithyanandham Singaravadivelu

Now I know about this issue.

You could only open the Exchange online related port. But, for Office 365 account, it may integrate with others Office 365 functions which used by Outlook client. I think the Exchange online could supported for most functions.

The Microsoft 365 Common and Office Online is used to Office Online Server (AKA OOS)

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

---