How to email an icalendar (ics) file

Im developing a RoR application, i'm using Ri_Cal to generate an ics file, i want to email this file as an attachment so people who receive it can add the events I'm sending to their calendar. I have tried attaching the file in an email but when 开发者_开发百科i open it with Mail.app in OSX it doesn't automatically ask if i want to add the event. I have to download etc. How can i archive this to be automatically?

Check if your ICS file has METHOD:PUBLISH or METHOD:REQUEST. The latter should trigger asking.

I want do this with mi app but Zimbra never detect METHOD:PUBLISH When I use Thunderbird for invite, Zimbra detect icalendar without problems.