Name: allowstarttls
Type: SWITCH
Default-Value: 0
Last-Modified: 3.12.1

If enabled, allows upgrading a plaintext connection to use TLS (a.k.a
opportunistic TLS) via a protocol specific command/mechanism.  IMAP, LMTP,
NNTP, and ManageSieve use the STARTTLS command.  POP3 uses the STLS
command.  HTTP uses the Upgrade header field.
