Forum Discussion
Signature displayed wrong in New Outlook on Mac
Because the signature is correct in Sent Items, do not rebuild it yet. Check whether Outlook is composing in a different appearance mode: temporarily set Outlook's appearance to Light and disable any message-background/theme option, then create a new message. If the preview changes while Sent Items remain correct, it is a compose-window rendering defect. Capture that comparison with the Outlook and macOS version for Microsoft support.
I can confirm the issue and add some more information:
Changing to Current (Preview) or Beta Update Channel in 16.110.1 changes the displayed "default" font from Times New Roman 12pt to Aptos 12pt. This may look like a fix to the thread owner but still ignores the font family and size set in the Signature editor.
On the receiving end there is mostly Aptos 12pt displayed execpt for answering on Windows New Outlook or on the web. Here the original Signature uses Segoe UI.
Maybe the intention was to "use a default font for every signature" but the diffrent environments use different fonts. Even if done correctly this should only aply to Signatures using the default font and not overwrite the font settings changed by the user.