This is necessary to allow for creative department based access control and
alerts.

If a non-text attachment specifies a charset in the content-type header,
don't transcode the content before saving it to the database. This can
corrupt attachments which have a header like the following:

Content-Type: application/pdf; charset=UTF-8

Since a PDF contains binary data, coercing it to UTF-8 encoding will drop
characters not valid in UTF-8 and will corrupt the attachment data.

Also support the TransportName in the properties list and prefer it over the
attachment-level attribute, as it is Unicode encoded.

The priority setting was broken when priority was added to the dynamic data

This is necessary to make sure session data is saved on redirect.

Previously, the data blocks were inspected byte for byte. Now data blocks
are parsed 1k at a time. Fewer PHP function calls ultimately means faster
performance.

This should speed up the system where several emails and alerts will be sent
through the same SMTP account in the same request.

If the system has only one help topic automatically select the help topic
and display any associated custom form.

Priority field and custom list fields have a prompt value (shows up only for
drop-down widget). And the short and long answer fields have a placeholder
configuration item.

This is needed to help us remove invalid characters set by some mail
clients.

Previously, the Delivered-To header was only used if the To header was not
found

If a wrapped mail is sent, copy the Delivered-To header into the nested
message so it will be clear(er) how the mail arrived into the system. Also,
copy the Message-Id into the nested mail if there is none to help against
mails delivered repeatedly.

Some emails providers (e.g gmail/google) won't deliver emails marked
bulk/autoreply to group email address.

Until we add text/plain bodies to the ticket thread without an enclosing
<pre> element, we should not treat the <pre> element like a code or
blockquote block.

On some combinations of operating systems, PHP and libpcre versions, `\s`
will match the iso-8859-x non-breaking-space, 0xa0. This regular expression
will munge the UTF8 encoded version, 0xc2a0 to 0xc220, which is not a valid
UTF8 character.

When inserted into a UTF8 field in mysql, the text will be truncated at and
after the first invalid character.

These functions don't appear to be used an could corrupt UTF-8 encoded text