I just encountered that you are not able to use for example G-Mail Integrations with a mirrored “E-Mail” Column from another board.
I personally use it to have one board (like a contacts list) and one board that i use to plan my freelance staff. Now I wanted to add an integration that would send a mail to my freelance staff, whenever i change their status to give them an update on their booking. Unfortunately the integrations window wont let me use the mirrored e-mail (or any other column). It seems like the integration does not see the mirrored e-mail column as an e-mail type column.
Would be great if this feature/bug would be fixed. This is also true for the twilio integration.