change the Mail flow from "on-prem" to Office365.

Question

Need to change the Mail flow from "on-prem" to Office365.
This is critical, because the existing On-Premise Email Gateway already Expired and not scanning.

mailboxes are hosted in Hybrid Exchange (70% on cloud – 30% at On-Prem Exchange 20219)
MX record currently pointing to On-Prem Exchange
I want to Change MX Pointer from On_prem to On-Cloud Exchange
On-Prem Email Gateway has expired
(On-Premise Email Gateway already Expired and not scanning) the smart-host (Symantec Email gateway) subscription has been expired therefore it stopped the inbound scanning.
domain is hosted locally (on-prem), (exchange also hosted on-prem but we migrated to hybrid-exchange since last 1 year)
it was working properly until we had valid subscription.
My requirement is to change the MX Pointer from ON-Prem to On-Cloud so that all inbound email directly land on Microsoft O365 tenant and scan.
Note: our existing smart host (on-prem) already expired and all on-prem users receiving emails without scanning.

I have been advised by a friend on this with the T/S steps
If registrar doesn't support adding TXT records, he informed I can verify by adding an MX record.

Sign in to the Microsoft 365 admin center and select Show all > Settings > Domains.
In a new browser tab or window, sign in to my DNS hosting provider, and then find where I manage your DNS settings (e.g., Zone File Settings, Manage Domains, Domain Manager, DNS Manager).
Go to my provider's DNS Manager page, and add the MX record indicated in the admin center to your domain.
This MX record's Priority must be the highest of all existing MX records for the domain. Otherwise, it can interfere with sending and receiving email. I should delete this records as soon as domain verification is complete.
I need to Make sure that the fields are set to the following values:

Record Type: MX
Priority: Set to any large value not used already.
Host Name: @
Points to address: Copy the value from the admin center and paste it here.
TTL: 3600 (or your provider default)
When Microsoft finds the correct MX record, your domain is verified.

Reference article
https://learn.microsoft.com/en-us/microsoft-365/admin/get-help-with-domains/create-dns-records-at-any-dns-hosting-provider?view=o365-worldwide#step-1-add-a-txt-or-mx-record-to-verify-you-own-the-domain

I would like to verify the “SFP,DKIM” configuration because we recently Disabled the “Central Mail Flow” where all email now going out directly from Exchange-Online.

How do I go for it?

Could you please help me with the exact steps

Answer 1

"I would like to verify the “SFP,DKIM” configuration because we recently Disabled the “Central Mail Flow” where all email now going out directly from Exchange-Online."

Did you create these records already ?

https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/use-dkim-to-validate-outbound-email?view=o365-worldwide

If so:

Go to mxtoolbox.com

enter your domain to verify the mx record.

then select the SPF check and enter your domain

then enter the DKIM check and enter your domain

Use this pattern

yourDOMAIN.com:selector1
yourDOMAIN.com:selector2