Use ProcessBuilder and Flow to evaluate attachments, AND get rid of the signature pictures! This will help your users quickly identify Salesforce Service Cases that has attachments, and reduce your storage waste.
The below solution does NOT scale, but it works if your case volume is in the thousands a day. What it does, is to analyze any incoming email post arrival. This is important as SalesForce cant currently do it on arrival, as it doesnt have the flags set yet.
To do this PostArrival, you have to use Scheduled Action. Preconditions in the below setup is Enchanced Email and Attachments as Files. The concept does work for the Attachment object as well though.
So 1 hour prior the email arriving, it kicks of a time based workflow from Process Builder, scans it for any non image attachments, and if so, updates a Case flag to show that it has attachments. It then kicks of a subflow, that kills any images less than 8kb.
Step 1 – Kick of the Scheduled Actions:
Kick of the Time Based Workflow 1 hour prior to the email arriving, if it has the Attachment flag set to True on the email.
Step 2 – Evaluate the Attachments:
Evaluate the Attachments for a PDF, txt, Excel etc based on fileextension first, so that the user gets the Case list updated with the Attachment flag.
Step 3 – Delete the Signature images:
Then delete all the garbage attachments. And do the world a favour, champion in your organizations to stop this bad practices, too many people still have embedded images in their email signature.
This problem has also been discussed in this thread over at SalesForce Trailblazer Community. Upvote the idea, as the above is not a good solution! In the case you have a incoming email burst, things can go haywire!
Should you have any feedback or improvement suggestions, let me know!