feature request: subscribe multiple folders at once.

[xxxmicrobexxx]

I am in the middle of importing mail for a customer. There are hundreds (!) of folders. When they are imported they are not subscribed by default. I am having to go through the list and subscribe them manually which is tedious to say the least.

It would be a good feature to be able to "select all" folders and do a mass subscribe.

[alecpl]

Duplicate of #5090.