Ironport Failing to update DNS changes??

[howardh]

We recently migrated a domain from an existing Office365 tenant to a new tenant with the same domain names and email accounts.

We made the cutover last weekend.

Everything mostly works, except we still cannot get or send messages to certain domains.     And with Microsoft's technical support - narrowed it down to domains that are protected by Ironport email security.

Why would Ironport not update DNS MX changes?    Is this a bug?    Is there a way to force a refresh or a flush of cached entries?    

Users at the remote domains get non-deliverable notices saying our domain is non-existent.

Yet the domain is properly registered with Cloudflare - and Microsoft has examined every trace of our tenant settings and DNS and says that it is just laggy updating on the individual security setups.

Thanks for any advice,

Howard

[aayalaga]

Hello Howard,

You can try the Clear Cache button from the GUI under Network > DNS, or the dnsflush command via CLI, it will clear all information in the DNS cache. You may choose to use this feature when changes have been made to your local DNS system. The command takes place immediately and may cause a temporary performance degradation while the cache is repopulated.

Regards