Useful evidence with narrower reach
A screenshot or PDF may record wording and appearance relevant to a dispute. It usually does not contain all the underlying message structure. A forwarded message may preserve quoted text while introducing new headers and omitting original properties. None should be discarded simply because a native source is unavailable.
Preserve provenance
Keep the original supplied files and record who produced them, from which account or device, and by what process. Retain surrounding screenshots or pages where relevant. Avoid cropping, annotating or converting the only copy. Identify potential account exports, local stores, attachments and other correspondents that may corroborate the content.
Set a proportionate question
An examiner may assess internal consistencies, compare versions and identify missing context, but cannot recreate omitted metadata by assertion. An apparent visual anomaly may have an ordinary rendering or conversion explanation. Begin with the allegation and the creation history of the surviving material. A preliminary assessment can state what can be examined now, which additional sources would materially help and whether a reliable conclusion remains unavailable.