Add new field and turn off subject

[otresi]

Otrs is working but a have a few question for you

1. In sytem log i got this error each 10 min

OTRS-otrs.Console.pl-Maint::PostMaster::MailAccountFetch-43

There was an error executing Execute() in Kernel::System::Console::Command::Maint::PostMaster::MailAccountFetch: ERROR: OTRS-otrs.Console.pl-Maint::PostMaster::MailAccountFetch-43 Perl: 5.16.3 OS: linux Time: Tue Dec 27 13:50:12 2016

2. How can i add field on customer page for phone? i added

Ticket::Frontend::CustomerTicketZoom###DynamicField field Phone with number 1
Ticket::Frontend::CustomerTicketMessage###DynamicField field Phone with number 1

but not work.
3. Is it possible to turn off subject field when i add note or close ticket?

Version otrs is 5.0.8

Thanks a lot