helpdesk software that works inside 
Emails received on a certain address are immediately sent to Trello. Threaded emails are kept within the same Trello card. Comments prefixed with the :email: emoji, 
, will be sent back to the submitter, as replies. Markdown is supported.
Comments without the prefix are not sent back, so you can discuss the issues internally.
You can get a quick glance of BoardThreads simplicity using just a few clicks and right now: send an email to [email protected], then breath deeply and watch as it appear in this board, after that you can reply in the card with a comment (prefixed by the :email: emoji, ) and you'll get the response in your email. Done.
It costs $18 / month for unlimited users, unlimited emails.
Sign up here and get an @boardthreads.com address linked to a Trello list.
The first 2 months are free.
Make your team work together on answering customers and creating the product.
Send or receive email through your custom email address. Add repliers to the card. Signature templates!
Since Trello is a well established product, there are a lot of extensions and apps that complete your Trello experience, from integrations with third-party services like Slack and GitHub to tools that make it easy to do time-tracking and generate useful reports. All these you can find at this official Trello page dedicated to integrations.
After that it costs only $18 / month for unlimited users, unlimited emails.
Sign up here and get an @boardthreads.com address linked to a Trello list.