Can you Use ‘Let’s Encrypt’ on Hybrid Exchange?
Jan07

Can you Use ‘Let’s Encrypt’ on Hybrid Exchange?

KB ID 0001770 Problem A few months ago I wrote an article about getting free exchange certificates with Lets ‘Encrypt’. And that still works peachy, I implemented it on my test Exchange 2019 server (in Hybrid mode) and all appeared well.  Some time later, (remember this is my test network so it’s not in production.) I noticed that mail was not getting forwarded from O365 to the on premises Exchange server. I’ve...

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Mail Routing Issue ‘451 5.7.3 Cannot achieve Exchange Server authentication’
Nov17

Mail Routing Issue ‘451 5.7.3 Cannot achieve Exchange Server authentication’

KB ID 0000791 Problem While putting in a New Exchange 2010 server today, I test moved a mailbox to this new site, and could not get mail to flow to the Exchange 2010 server at the clients main site. 451 4.4.0 Primary target IP address responded with: “451 5.7.3 Cannot achieve Exchange Server authentication.” Attempted failover to alternate host , but that did not succeed. Either there are no alternative hosts, or delivery...

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