Routinely I’ve been dealing with Outlook meeting invitations. Simply replying and accepting a meeting over the phone or in email isn’t good enough. It doesn’t list me as a confirmed attendee in their calendar itself. This can lead to unfortunate confusion.
Because of this, and that I received another invitation I did not want to be misconstrued, I found a reasonable solution to this problem.
I have been a Thunderbird user for a number of years. Initially the reason I switched to it from mutt was for the ease of encryption (with enigmail) and early TLS auth abilities that I needed early on for a project. Since then, at the time it was Mozilla’s combined email and web client, Thunderbird has done a great job with the internal PKI signed Microsoft encrypted mail (send by some in the consulting companies of which I have been a member) and many other tasks that have given other mailers problems.
Even though Lightning is still a bit clunky, it is workable for properly formatting Outlook responses.
With Provider, you can sync your calendar data with a google calendar. Which, in turn, ical can subscribe to google calendars, which is then synced to my smartphone. I have found that the multisync methods and software currently available, like gsync, spanning sync, multisync, or missing sync, to not be worth the trouble so far, so this is my pick at this time.
I am already able to sync ical with my google calendar for some time using this simple method. One thing to keep in mind here is that google calendar is public world facing information, so take some time to think about if this works for the implementation you are considering.