docs: git-send-email: difference between ssl and tls smtp-encryption

New explanation for the difference between these values.
It's hard to understand what they do based only on the names.
New description of used default ports.

Signed-off-by: Sotir Danailov <sndanailov@wired4ever.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/git-send-email.txt b/Documentation/git-send-email.txt
index 3290043053aa6d16f6a0d63f1c9a04e54e349e36..765b2df8530d1fc3426b75cb266b2f2213278d19 100644 (file)
--- a/Documentation/git-send-email.txt
+++ b/Documentation/git-send-email.txt
@@ -178,9 +178,18 @@ Sending
        for `sendmail` in `/usr/sbin`, `/usr/lib` and $PATH.
 
 --smtp-encryption=<encryption>::
-       Specify the encryption to use, either 'ssl' or 'tls'.  Any other
-       value reverts to plain SMTP.  Default is the value of
-       `sendemail.smtpEncryption`.
+       Specify in what way encrypting begins for the SMTP connection.
+       Valid values are 'ssl' and 'tls'. Any other value reverts to plain
+       (unencrypted) SMTP, which defaults to port 25.
+       Despite the names, both values will use the same newer version of TLS,
+       but for historic reasons have these names. 'ssl' refers to "implicit"
+       encryption (sometimes called SMTPS), that uses port 465 by default.
+       'tls' refers to "explicit" encryption (often known as STARTTLS),
+       that uses port 25 by default. Other ports might be used by the SMTP
+       server, which are not the default. Commonly found alternative port for
+       'tls' and unencrypted is 587. You need to check your provider's
+       documentation or your server configuration to make sure
+       for your own case. Default is the value of `sendemail.smtpEncryption`.
 
 --smtp-domain=<FQDN>::
        Specifies the Fully Qualified Domain Name (FQDN) used in the