Clarify password encryption (#452)

Clean up sentence structure and clarify the language around
passwords being sent over TLS.

Co-authored-by: Mark W <mark@digitalnotions.net>

docs/client/client-manual.en.md

@@ -11,7 +11,7 @@ These instructions are valid for unchanged port bindings only!
 |SMTP|STARTTLS|<span class="client_variables_available"> <code><span class="client_var_host"></span><span class="client_var_port"></span></code></span><span class="client_variables_unavailable">mailcow hostname</span>|587|
 |SMTPS|SSL|<span class="client_variables_available"> <code><span class="client_var_host"></span><span class="client_var_port"></span></code></span><span class="client_variables_unavailable">mailcow hostname</span>|465|
 
-Please use "plain" as authentication mechanisms. Contrary to the assumption no passwords will be transferred plain text, as no authentication is allowed to take place without TLS.
+Please use the "plain" password setting as the authentication mechanism. Contrary to what the name implies, the password will not be transferred to the server in plain text as no authentication is allowed to take place without TLS.
 
 ## Contacts and calendars
 
@@ -20,4 +20,4 @@ SOGos default calendar (CalDAV) and contacts (CardDAV) URLs:
 1. **CalDAV** - https://mail.example.com/SOGo/dav/user@example.com/Calendar/personal/
 2. **CardDAV** - https://mail.example.com/SOGo/dav/user@example.com/Contacts/personal/
 
-Some applications may require you to use https://mail.example.com/SOGo/dav/ _or_ the full path to your calendar, which can be found and copied from within SOGo.
+Some applications may require you to use https://mail.example.com/SOGo/dav/ _or_ the full path to your calendar, which can be found and copied from within SOGo.