Add Date: header for sendmail*.conf actions

According to rfc2822, Date: headers are not optional.
Added these to all sendmail action templates, format specification
should conform to rfc and be portable across multiple platforms.

config/action.d/sendmail-whois-lines.conf

@@ -12,6 +12,7 @@
 # Values:  CMD
 #
 actionstart = printf %%b "Subject: [Fail2Ban] <name>: started
+              Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
               From: Fail2Ban <<sender>>
               To: <dest>\n
               Hi,\n
@@ -24,6 +25,7 @@ actionstart = printf %%b "Subject: [Fail2Ban] <name>: started
 # Values:  CMD
 #
 actionstop = printf %%b "Subject: [Fail2Ban] <name>: stopped
+             Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
              From: Fail2Ban <<sender>>
              To: <dest>\n
              Hi,\n
@@ -46,6 +48,7 @@ actioncheck =
 # Values:  CMD
 #
 actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip>
+            Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
             From: Fail2Ban <<sender>>
             To: <dest>\n
             Hi,\n

config/action.d/sendmail-whois.conf

@@ -12,6 +12,7 @@
 # Values:  CMD
 #
 actionstart = printf %%b "Subject: [Fail2Ban] <name>: started
+              Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
               From: Fail2Ban <<sender>>
               To: <dest>\n
               Hi,\n
@@ -24,6 +25,7 @@ actionstart = printf %%b "Subject: [Fail2Ban] <name>: started
 # Values:  CMD
 #
 actionstop = printf %%b "Subject: [Fail2Ban] <name>: stopped
+             Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
              From: Fail2Ban <<sender>>
              To: <dest>\n
              Hi,\n
@@ -46,6 +48,7 @@ actioncheck =
 # Values:  CMD
 #
 actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip>
+            Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
             From: Fail2Ban <<sender>>
             To: <dest>\n
             Hi,\n

config/action.d/sendmail.conf

@@ -12,6 +12,7 @@
 # Values:  CMD
 #
 actionstart = printf %%b "Subject: [Fail2Ban] <name>: started
+              Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
               From: Fail2Ban <<sender>>
               To: <dest>\n
               Hi,\n
@@ -24,6 +25,7 @@ actionstart = printf %%b "Subject: [Fail2Ban] <name>: started
 # Values:  CMD
 #
 actionstop = printf %%b "Subject: [Fail2Ban] <name>: stopped
+             Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
              From: Fail2Ban <<sender>>
              To: <dest>\n
              Hi,\n
@@ -46,6 +48,7 @@ actioncheck =
 # Values:  CMD
 #
 actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip>
+            Date: `date -u +"%%a, %%d %%h %%Y %%T +0000"`
             From: Fail2Ban <<sender>>
             To: <dest>\n
             Hi,\n