Posted on 2 December 2025

Why attaching your corporate logo and banners in email signatures is a bad idea

If Outlook shows image001.png as an attachment, or Gmail puts a paperclip on a message that has no file, the logo in your signature is almost certainly travelling as a real attachment instead of a hosted image.

That is not a design choice. It is how many email clients, and most copied-and-pasted signatures, still work. The graphic looks like part of the layout on your screen. In the raw message it is a MIME attachment, duplicated for every recipient, every time.

What actually goes wrong

The paperclip lies

Recipients scan for attachments. When the list already contains image001.jpg, image002.png, and a social icon, a real PDF is easy to miss. Mobile clients make this worse: they show a generic attachment badge on the thread even when you only sent a signature.

Every send copies the file

An attached logo is not one file sitting on a server. It is a new copy stuffed into each outbound message. High-volume teams fill mailboxes with identical logos. Replies and forwards pile up more copies. Nothing about that is required for the logo to display.

Spam filters notice bulk graphics

Filters do not hate logos. They hate bulk mail that looks like a flyer. A huge attached banner, plus social icons, plus a tracked pixel, is a stronger junk signal than a small hosted logo in a simple HTML table. You can still land in spam for other reasons. Attached banners just make the job easier for the filter.

It is a wasteful way to show a brand

The same PNG is uploaded and downloaded thousands of times a week even though the recipient already has it. Hosted images can be cached. Attachments cannot in any useful way. If you already dropped the please consider the environment line because it added empty bytes, attached logos are the bigger leak.

Host the image instead of attaching it

A proper HTML signature points at a URL. The message carries a short img src, not the file. The recipient’s client fetches the logo from a host (Mirosign uses Cloudinary). After the first view, many clients reuse a cached copy.

1. Design the signature as HTML, not as a screenshot from Canva pasted into Outlook.
2. Load the logo and banner from a stable HTTPS URL. Do not embed them with Outlook’s Insert Picture.
3. Keep the file small. A sharp logo at the size it actually displays beats a 2000px banner scaled down in the client.
4. Install the HTML in each client the way that client expects. Outlook, Gmail, and Apple Mail are not the same dialog.

Step-by-step for the attachment symptom: how to stop the logo showing as an attachment. If you already use Mirosign and still see a paperclip, start there rather than rebuilding the design.

Why your email signature logo shows as an attachment

Because the image was embedded in the message. Outlook is the usual culprit: paste, Insert Pictures, or a Word-based signature all tend to attach. Gmail for web is cleaner if you paste HTML, and messier if you paste a picture. The fix is not a smaller JPEG. It is a hosted file and HTML that points at it.

Design a hosted signature in Mirosign if you want that to be the default, not a workaround.