Hello,

I'm wondering how you can set up a hybrid SmarterMail / Office 365 environment where one email address is hosted at Office 365 (Exchange Online) and the others are hosted with SmarterMail? This used to work OK at our previous ISP using a different email server, but since moving to the new ISP (using SmarterMail 17 Pro) the Office 365 user gets an error when sending to the locally hosted domain.For example, let's say the domain in question is my-domain.com and bob@my-domain.com is the Office 365 email user. When email comes in to bob@my-domain.com it gets forwarded to the Office 365 email account. That works fine. When Bob emails joe@my-domain.com he gets a rejection email back "bob is not authorized to relay messages through the server that reported this error, 550 5.7.368 Remote server returned authentication required to relay". When Bob emails any domain not configured in SmarterMail the email goes through just fine.

After doing some investigation, it looks like Office 365 (Exchange Online) allows you to create a "send connector" which allows TLS authentication using a client certificate, but there doesn't appear to be anyway to make use of this in SmarterMail. Unfortunately, there is no way in Office 365 to set up a send connector using basic authentication (username/password) which is what would work for SmarterMail.

I'm wondering if anyone has an idea of how to make this work? I found the temporary solution of turning off "Require SMTP authentication", but I know that this is not a good long-term solution since it leaves the domain open to email spoofing. I've opened support tickets with my ISP and also with Microsoft, but so far haven't been able to find a workable solution.

Thanks.