Tal Raviv

Popping in here to add an alternative method: use Slack's email forwarding feature

On Slack, open your Preferences and go to
Messages &Media.
Scroll all the way down to the
Bring Emails into Slack section.
Click the Get a Forwarding Address and copy the e-mail address.

 

On Gmail, open your
settings and go to
Forwarding and POP/IMAP.
Click on
Add a Forwarding Address and paste the address you copied from Slack. Click Proceed.

From there, you can create a search filter and have it forward to your slack address.