| Value |
Description |
| smtpOptionNone |
No additional options are specified when establishing a
connection with the server. A standard, non-secure connection
will be used and the client will not attempt to use extended
(ESMTP) features of the protocol. Note that if the mail server
requires authentication, the smtpOptionExtended option
must be specified. |
| smtpOptionExtended |
Extended SMTP commands should be used if possible. This
option enables features such as authentication and delivery
status notification. If this option is not specified, the
library will not attempt to use any extended features. This
option is automatically enabled if the connection is
established on port 587 because submitting messages for
delivery using this port typically requires client
authentication. |
| smtpOptionTunnel |
This option specifies that a tunneled TCP connection and/or
port-forwarding is being used to establish the connection to
the server. This changes the behavior of the client with
regards to internal checks of the destination IP address and
remote port number, default capability selection and how the
connection is established. |
| smtpOptionTrustedSite |
This option specifies the server is trusted. The
server certificate will not be validated and the connection
will always be permitted. This option only affects connections
using the TLS protocol. |
| smtpOptionSecureExplicit |
This option specifies that a secure connection should be
established with the server and requires that the server
support the TLS protocol. This option initiates
the secure session using the STLS command. |
| smtpOptionSecureImplicit |
This option specifies the client should attempt to
establish a secure connection with the server. It should only
be used when the server expects an implicit TLS connection or
does not implement RFC 2595 where the STLS command is used to
negotiate a secure connection with the server. |
| smtpOptionSecureFallback |
This option specifies the client should permit the use of
less secure cipher suites for compatibility with legacy servers.
If this option is specified, the client will allow connections
using TLS 1.0 and cipher suites that use RC4, MD5 and SHA1. |
| smtpOptionPreferIPv6 |
This option specifies the client should prefer the use of
IPv6 if the server hostname can be resolved to both an IPv6 and
IPv4 address. This option is ignored if the local system does
not have IPv6 enabled, or when the hostname can only be resolved
to an IPv4 address. If the server hostname can only be resolved
to an IPv6 address, the client will attempt to establish a
connection using IPv6 regardless if this option has been
specified. |