imap-process-connection-type

imap-process-connection-type is a variable defined in `imap.el'.
Its value is

nil

Documentation:
Value for `process-connection-type' to use for Kerberos4, GSSAPI, shell, and SSL.
The `process-connection-type' variable controls the type of device
used to communicate with subprocesses. Values are nil to use a
pipe, or t or `pty' to use a pty. The value has no effect if the
system has no ptys or if all ptys are busy: then a pipe is used
in any case. The value takes effect when an IMAP server is
opened; changing it after that has no effect.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 22.1 of Emacs.