9.1.4. Advanced

These settings define miscellaneous OpenPGP and Enigmail options.

Enable Encrypt replies to encrypted message if you want Enigmail to automatically switch on encryption when composing a reply to an encrypted message. This is a smart thing to do, especially if you quote the original message.

Add Enigmail comment in OpenPGP signature adds the comment line
Comment: Using GnuPG with Mozilla –http://enigmail.mozdev.org/
to the OpenPGP signature block.
Note that you can add any comment to the OpenPGP signature by calling GnuPG with the parameter --comment your_comment (see below to learn how to specify additional parameters to the GnuPG executable).

When signing, lines starting with a dash (-) are replaced with two dashes separated by a space (- -) according to the OpenPGP standard. This however makes a double-dash line (--) no longer appear as a separator between the message body and a personal signature, usually displayed in grey.
By enabling the option '--' is a signature separator, Enigmail makes some workaround to correctly handle the signature separator when reading and composing messages.

Use gpg-agent for passphrases tells Enigmail to use gpg-agent, the GnuPG passphrase agent, to cache the passphrase; this tool is especially useful if you use several passphrases. Do not activate this option if you want Enigmail to ask you for your passphrase.

GnuPG version 2.0.x is distributed with gpg-agent. Enabling this option makes Enigmail use gpg-agent also for GnuPG version 1.4.x (this requires the gpg-agent and pinentry tools to be installed).
Note that some distributions install Seahorse instead of gpg-agent, and this may cause problems when using OpenPGP smart cards. If you use a smart card for your key, then either use gpg-agent and enable this option, or unset it and make sure the environment variable GPG_AGENT_INFO is unset prior to starting Enigmail (since GnuPG expects gpg-agent to be running once it detects that this variable is set). See also FAQ entry 11.8.

Use '<' and '>' to specify email addresses. Usually, email addresses are surrounded by angle brackets (< >) to separate the full name part from the email part, e.g. John Random Hacker <jrhacker@example.com&gh;.
Deactivating this option removes the brackets from email addresses. This is necessary to ensure compatibility with some provider service, like Hushmail, that does not support brackets in email addresses. Hushmail is a provider for OpenPGP encryption over the web, but keys generated with Hushmail are not fully compatible with OpenPGP.
This option should be normally turned on when encrypting, as Enigmail relies on it to avoid potential confusions and hence security problems, but needs to be turned off for Hushmail keys.

Hide SMIME buttons/menus hides the S/MIME button from the toolbar of the mailclient interface. This option exists only on SeaMonkey 1.1, because Thunderbird and SeaMonkey 2.0 and higher allow the user to customize the whole toolbar. This option, if it exists, is enabled by default in order to avoid confusing users.

Only download attachments when opened (IMAP only) enables an IMAP feature that makes Thunderbird / SeaMonkey download only the first 35-40 Kb of a message, downloading attachments only on demand. However, if an encrypted message is larger than this size, it may happen that it is downloaded only in part, its end will be missing, and hence Enigmail will fail to decrypt it.
If you use an IMAP inbox, and notice that Thunderbird / SeaMonkey sees some of your mails as broken or reports an error when trying to decrypt them, disable this option. The mailclient will then download the complete message at once.
Alternatively, you can click on the broken lock to download the message in full.
This problem often happens with Thunderbird 2. It should not appear with Thunderbird 3, which by default downloads the whole message.

The text field Additional parameters for GnuPG allows you to have Enigmail call the GnuPG executable with the parameters you prefer. For instance, the figure in this section shows the additional parameters --homedir X:\gnupg being passed to GnuPG; this tells GnuPG to go look for the keyrings in the X:\gnupg directory instead of the default directory.

Finally, the Reset Warnings button controls the way Enigmail pops up the interactive dialogs asking you to make a choice. If you ever asked Enigmail to remember your choice for the future (for instance when choosing how Enigmail should sign/encrypt attachments), clicking this button will have Enigmail prompt you the dialog again when needed.