I've recently started using Mandrill for sending transactional emails to our customers and staff. The emails are addressed so that they are sent from name<_at_>ourcompany.com

We still continue to use Kerio Connect 9.2.10 for all other email sending and receiving for our company.com

This all works fine except when the Mandrill recipient is within our organisation (ie person<_at_>ourcompany.com)

Because I have sender anti-spoofing protection turned on (to stop outside organisations sending email pretending to come from us), the mail sent from Mandrill is blocked:

[09/Sep/2019 17:34:36] SMTP: Message from IP address x.x.x.x was rejected because of missing authentication for local domain sender <name<_at_>ourcompany.com>.

Because Mandrill uses an ever-changing IP address range, I can't simply add their IP address range to the whitelist - so right now the only option I can see is to turn off the anti-spoofing protection.

Has anyone got any ideas how to work around this?

Thanks!

Thanks Jon. The problem is that the IP address range for Mandrill could change (and indeed they warn that it probably will).

If I use their existing IP address range then mail could suddenly start bouncing if they add another IP address.

So I'm stuck...

Cheers

James