[Enigmail] v0.95.4 on OS X?

[Olav Seyfarth]

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Hi Matthew,

> gpg: skipped "<mmacleod at ieee.org>": unusable secret key
> gpg: [stdin}: clearsign failed: unusable secret key

this does not look like an Enigmail problem but a GnuPG problem. Please
verify that it isn't by trying to sign something using gpg directly from
the command line.

If it were Enigmail's fault: is the correct key selected for signing?
If you have multiple keys with that email address on them as one of their
UIDs, you should rather select the key to sign with explicitely:

- - in Account settings, go to 'OpenPGP Security' settings
- - there, use the button "Select Key ..." to explicitely select a key by
  its KeyID

- - repeat this step for all identities of each account (where you want to
  use OpenPGP); Identities' settings can be accessed though the account's
  main settings page (the one above 'Server settings') using the button
  'Additional Identities ...' (or something similar) at the bottom.

Olav
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