10,000 list ".gov" email send issue

Regular Participant
Anyone else having issues with Constant Contact sends?
We manage a list of 10,000 that gets sent as a "gov" email and things have been fine for months.
But the latest email won't send. It's not a content issue. Constant Contact seems to be struggling to send as certain email types as per the Microsoft 365 / Outlook changes lately.
And they are telling me that we need to ask this client to establish DKIM key authentication, which "might fix it".
Oh and then we lose the ability to send as anything other than this specific "gov" address, crippling the account.
What is going on with this?
Are we alone here? Is another platform the answer?
Thank you!!
PS We only manage one other list and that is our own internal one. We're not a marketing company. Thanksss!

Hello @Pennoni ,


Most email security systems, especially for government, company, and other large organizations, prefers authentication from one server as a means of mitigating spam and avoiding malware - even if the ESP being sent from is trusted. You can only have one domain authenticated per account. Unfortunately, this is just how emails work for these larger entities nowadays, regardless of which ESP is used.


If you need more info on self-authentication, and the processes involved


Deliverability's numbers and hours if you need more specialized guidance

William A
Community & Social Media Support

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