Category: spf
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Improving Exchange Online Email Deliverability Through Third Party Filtering Services – Trusted ARC Sealer
When you receive emails into Exchange Online and you filter the external messages before arrival with a third party filter such as Mimecast, Proofpoint or others, then you can have DMARC failures that result in messages being junked or quarantined in Exchange Online. Trusted ARC Sealer is a feature of Exchange Online to allow you…
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Gmail showing “via” in Microsoft 365 Email Headers
I came across this issue the other day. In the headers of an email received from Microsoft 365 / Exchange Online into Gmail (and not other recipients) the message header reads “name@domain via otherdomain.onmicrosoft.com”, for example: In this case the via header for onmicrosoft.com was an old organization name and as tenant rename does not…
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Outbound Email Via Exchange Online Protection When Using Hybrid Exchange Online
In a long term hybrid scenario, where you have Exchange Online and Exchange Server configured and mailboxes on both, internet bound email from your on-premises servers can route in two general ways. The first is outbound via whatever you had in place before you moved to Office 365. You might have configured Exchange Online to…
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DMARC Quarantine Issues
I saw the following error with a client the other day when sending emails from the client to any of the Virgin Media owned consumer ISP email addresses (virginmedia.com, ntlworld.com, blueyonder.com etc.) mx3.mnd.ukmail.iss.as9143.net gave this error:vLkg1v00o2hp5bc01Lkg9w DMARC validation failed with result 3.00:quarantine In the above, the server name (…as9143.net) might change as will the value…