# Class type Netmime.mime_header

    class type mime_header = object .. end

A MIME header with both read and write method. It is still possible, however, to set the read-only flag to make this kind of header immutable, too.
Inherits

- `Netmime.mime_header_ro` Supports all these read access method, too

    method ro : bool

whether the header is read-only or not

    method set_fields : (string * string) list -> unit

    method update_field : string -> string -> unit

    method update_multiple_field : string -> string list -> unit

    method delete_field : string -> unit

These methods modify the fields of the header. If the header is read-only, the exception `Immutable` will be raised.

`set_fields` replaces the current fields with a new list of (name,value) pairs. `update_field name value` replaces all fields of the passed name with the single setting (name,value), or adds this setting to the list. `update_multiple_field name values` replaces all fields of the passed name with the list of values, or adds this list. Finally, `delete_field name` deletes all fields of the passed name. Nothing happens if there is no such field.

Both `update_field` and `update_multiple_field` first replace existing values by the new ones without changing the order of the fields in the header. Additional values are inserted after the last existing value, or at the end of the header.