Ask HN: Better e-mail support interface?

I've been handling app support through an ordinary e-mail inbox and Thunderbird for years now, but it's slowly becoming unmanageable with volume increasing. Finding past e-mails is a pain and there's constantly a mail or two that slips through the gaps and goes unanswered.

What solutions would you recommend? I signed up for a Freshdesk trial but the configuration options are rather scary and complex.