Signing error sending from secondary UID [ multiple account setup ]

[jayaura]

My situation:

Thunderboird set up for 2 email address, A and B. I have generated a key pair with A as the primary account. I've added other UIDs : address B, and a new one C, which also I own, but not set up in thunderbird. Both accounts in thunderbird (A and B) set up for signing all mails by default. No encryption by default

The problem:

I got an email to my account B. So I want to reply to the same from account B itself, and I would like the reply to be signed. When I proceed as usual, without changing any settings and finally send the mail, thunderbird says "Error: Send option aborted. Encryption failed"

How can I fix this ? I belive the problem is because the key used to sign is having A as the primary email, yet I am sending it from B, which is a secondary UID. Does this matter ?

[Patrick Brunschwig]

I'd recommend you select the key in the account settings, not the email address. (Tools > Account Settings > OpenPGP Security --> Use specific OpenPGP key ID. You should do this for all accounts and all identities.

[jayaura]

Thank you Patrick, the issue is solved. I apprecite your help.