Compatibility

Outlook Classic for Windows (Outlook 2016, 2019, 2021, and the version that ships with on-prem Microsoft 365 installs) renders HTML signatures through the Word rendering engine. This means support for advanced CSS is limited, and Outlook Classic caches images locally when you paste a signature — a critical caveat that breaks dynamic CTAs.

Before you start

• Open Outlook Classic for Windows (look for “Outlook” in the Start menu — the icon is usually a yellow-and-white envelope).
• Have your Sigent.ai install link ready.
• Important: if you plan to update your signature’s CTA banner or assets later, read the CTA caching caveat below before proceeding.

Steps

1. Click your install link and choose Copy to clipboard.
2. In Outlook, click File → Options → Mail → Signatures… (the Signatures button is usually mid-page in the Mail settings).
3. Click New and give the signature a name.
4. Click into the editor below and paste with Ctrl + V.
5. Under Choose default signature, select your email account on the right.
6. Set the new signature for New messages and Replies/forwards.
7. Click OK twice to save and close.

Alternative: from any open email composer, click Insert → Signature → Signatures… to reach the same dialog.

Verify your signature

Compose a new message and verify the signature appears. Send a test to yourself and open it in Gmail Web — if colors, tables, and images render in both Gmail and Outlook, you’re good. Pay special attention to image dimensions; Outlook Classic occasionally adds extra spacing around images.

Troubleshooting

• CTA banner doesn’t update after I change it in Sigent. This is the most important caveat for Outlook Classic. Outlook caches images locally when you paste a signature. Updates on your Sigent dashboard do not propagate to Outlook Classic until you re-paste the signature. Workaround: re-install the signature monthly or whenever you update assets. We’re exploring auto-refresh patterns for Phase 2.
• Outlook is using Word formatting and breaking my layout. Outlook Classic renders all HTML through Word. Avoid flex, grid, and absolute positioning. Sigent’s templates use tables specifically because tables are the only reliable layout primitive in Word.
• Images appear but are sized wrong. Outlook Classic ignores CSS max-width and respects only the HTML width and height attributes. Sigent sets explicit attributes on all images for this reason.
• Trust Center → Automatic Download is blocking my images. Go to File → Options → Trust Center → Trust Center Settings → Automatic Download and either disable the “Don’t download pictures” option or add sigent.ai (or your custom CDN domain) to the safe senders list.
• The signature appears with a strange line height in replies. Outlook Classic uses mso-line-height-rule for table rendering. Sigent injects an MSO-conditional comment in the output to fix this; if you’re still seeing issues, re-paste a fresh copy from the install link.
• My company uses signature management software (Exclaimer, CodeTwo, etc.) and Outlook Classic. Server-side signature appenders intercept outbound mail at the Exchange level and replace the signature before delivery. Sigent’s signature applies only when composing locally — server appenders will override it. Coordinate with your IT admin if both are in use.

Notes

Outlook Classic is the trickiest client in our matrix because of the Word rendering engine and the image cache. If you can install in Outlook Classic without issues, every other client will work. If you only use the new Outlook (post-2024), follow the Outlook Modern guide instead — it’s much closer to Outlook on the Web.

Need help? Contact support — we usually respond within 24 hours.