Always sign and encrypt your emails
To maintain the security of conversations around support requests, you should always sign and encrypt your email to email@example.com if you have a Redmine account.
Our server is configured to reject emails that do not have a valid signature. We cannot reject unencrypted emails due to a limitation in the Redmine-OpenPGP plugin we are using, but we are logging them and will harangue you if you send us unencrypted email.
PGP/MIME vs. inline PGP
When you're replying to Redmine via email, you must use PGP/MIME instead of inline PGP. The default settings for the Enigmail plugin in Thunderbird should work.
Check your mail client and GPG integration tool's settings to ensure you are using PGP/MIME. One notable exception to this is Mailvelope, which cannot send PGP/MIME (you shouldn't be using Mailvelope anyway).
You may not want to use these settings (PGP/MIME, always sign) for all of your email. If not, most email clients support the concept of "Per-recipient rules", which allow you to configure specific settings on a per-recipient basis.
Below is an example of how to configure a per-recipient rule for firstname.lastname@example.org in Thunderbird/Enigmail. If you are not using Thunderbird/Enigmail, consult your mail client's documentation.
To check your global settings, go to Edit > Account Settings in Thunderbird. Navigate to the "OpenPGP Security" tab of the email account you are using for your Redmine account. Be sure that "Use PGP/MIME by default" is checked. If you do not want to enable "Sign messages by default" for everything, you should add a per-recipient rule for email@example.com.
To do so, go to Enigmail > Edit Per-Recipient Rules > Add, and enter firstname.lastname@example.org. Set to Apply rule if "Contains" the above address, select our key, change all of the defaults (Encryption, Signing, PGP/MIME) to "Always", then click OK, and OK again. The per-recipient rule should look like this: