When using Inbound Message Processing (tool_messageinbound), Moodle 4.5 encounters fatal errors while parsing certain emails that:

• Have incomplete MIME body structures, where expected array keys (e.g., $partstructure[2], $partstructure[5]) are missing.

• Do not specify a CHARSET in their MIME headers.

Proposed Solution:

Missing MIME Structure Keys: Use defensive checks to ensure safe defaults:
admin/tool/messageinbound/classes/manager.php
Line 755:

$attributes = isset($partstructure[2]) && is_array($partstructure[2]) ? $partstructure[2] : [];

$parameters = $this->process_message_body_structure_parameters(

    attributes: $attributes,

    parameters: $parameters,

);

Missing CHARSET: Default to 'UTF-8' when CHARSET is not provided:

admin/tool/messageinbound/classes/manager.php
Lines 779 and 786

charset: $parameters['CHARSET'] ?? 'UTF-8',