smtp.office365.com - fw rule

Hello MOl,

Thank you for reaching out to the community, ensure the fw rule created is on the top !
You can also add them into the exceptions:
1.) Office 365 URLs and IP address ranges - https://docs.microsoft.com/en-us/microsoft-365/enterprise/urls-and-ip-address-ranges?view=o365-worldwide
2.) Configure web exceptions for Office 365 - https://support.sophos.com/support/s/article/KB-000038173?language=en_US

Hello #Vivek,

I already have this and do not have any affect.

Main problem is that firewall rule (with fqdn "smtp.office365.com as destination) will not match all IPs from dns resolve of fqdn "smtp.office365.com"

MOl

Okay MOl, 

What are the DNS configurations on the SFOS under the network > DNS ? Can you please share ?

DNS1: 8.8.8.8

DNS2: 185.43.135.1

DNS3: 1.1.1.1

this is not issue.

Look at screenshoot. In FW log you can see IPs "40.99.150.82 & 40.99.150.66" as destination.

You can found both IPs in second screenshoot.

so DNS lookup from FW is working OK.

Okay, now can you share the FW rule screenshot ?

at this moment i have two rules

       - first with "smtp.office365.com" as destination

      - second  with "any" as destionation.

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Hello MOl,

Can see you have mentioned the service explicitly mentioned as only SMTPS and office also utilizes https and http ports. 
Try adding those services and ensure in the FW rule a "Linked NAT" is present with MASQ enabled ! 

Hello #Vivek,

I am talking about outgoing mail communication only. No need to add HTTP/S 

Hello #Vivek,

If you look at firewall log screenshot. We are talking about outgoing TCP 587 port, only .....

okay MOl, noted but have you created a LINKED NAT in the current FW rule with MASQ?