An IMAP account. mailtool will prompt for the login password.

An IMAP account accessed via an encrypted SSL connection.

A POP3 account. mailtool will prompt for the login password.

A POP3 account accessed via an encrypted SSL connection.

A local maildir mailbox. path specifies the maildir's location relative to the home directory (NOT the current directory).

Local mbox mail folders. path specifies the path to an mbox folder file, or a directory containing mbox folders, relative to the home directory (NOT the current directory).

Local mbox mail folders, like “mbox:path”; additionally, the system spool mailbox is automatically copied to $HOME/Inbox, which is accessible as folder INBOX.

Do not open the account unless the server supports secure password authentication. Secure password authentication verifies the account's password using a challenge/response authentication mechanism (where the label "cram" comes from). The actual password is never actually transmitted to the server, and therefore cannot be intercepted while in transit over an untrusted network.

Secure password authentication is not supported by all servers. This option may not work with some servers. This option does not enable secure password authentication, it only mandates its use. If the server supports secure password authentication, it will be used even without the /cram option. Traditional userid/password authentication will be used only if the server does not implement secure password authentication. The /cram option makes secure password authentication mandatory.

The /cram option is marginally useful even with encrypted server connections. The secure password authentication never sends the explicit password to the server. Encryption makes it theoretically impossible to recover the password from an encrypted data connection; but with secure authentication the password is never sent over the connection in the first place (the password's validity is certified by exchanging certain mathematical calculations between the server and the client). If the server is compromised, the compromised server will not receive the account password (unless the password is recovered from the server in other ways).

Do not use the SMAP if the server claims the availability of this experimental mail access protocol, and fall back to IMAP compatibility mode (this option is meaningful only with “imap://” and “imaps://” URLs).

Do not upgrade a plain connection to an encrypted one. This option is primarily used for testing and debugging purposes. Sometimes this option might be useful with servers that claim to offer encryption, but are unable to do so when taken up on their offer.

Do not validate the server's SSL certificate when using an encrypted connection. Normally the mail server's SSL certificate must be validate when using an encrypted connection. The certificate's name must match the server's name, and the certificate must be signed by a trusted certificate authority.

The encrypted connection normally fails if the certificate cannot be validate. Validation requires that a list of trusted certificate authorities must be known and configured. It's simply impossible to know which certificate authorities are valid without an explicit list of valid, known, trusted, certificate authorities. If a trusted authority list is not configured, no certificate can be validated. If the server's certificate is a self-signed certificate (this is often used for testing purposes), or if it's not signed by a known authority, the encrypted connection fails.

This /novalidate-cert option disables certificate validation. The encrypted connection will be established even if the server's certificate would otherwise be rejected.