possible options for a secure connection using TLS
either DISABLED, OPTIONAL or REQUIRED
DISABLED means STARTTLS will not be used in any case
OPTIONAL means STARTTLS will be used if the server supports it and a plain connection will be used otherwise;
please note that this option is not as secure as it seems since a MITM attacker can remove the STARTTLS line
from the capabilities reply.
REQUIRED means that STARTTLS will be used if the server supports it and the send operation will fail otherwise
possible options for a secure connection using TLS
either DISABLED, OPTIONAL or REQUIRED
DISABLED means STARTTLS will not be used in any case
OPTIONAL means STARTTLS will be used if the server supports it and a plain connection will be used otherwise; please note that this option is not as secure as it seems since a MITM attacker can remove the STARTTLS line from the capabilities reply.
REQUIRED means that STARTTLS will be used if the server supports it and the send operation will fail otherwise