Apple Mail signature font keeps changing? Fix it in Settings

Apple Mail can take a signature’s font from your message settings. The fix is usually one setting: in the Signatures pane, untick “Always match my default message font”, rebuild the signature, and send a test. If recipients still see the wrong size, the signature may carry formatting from the paste.

Why Mail changes the signature font

Apple’s Mail guide says that when a signature uses the message font, it takes the font set in Fonts & Colors. So the font comes from your message settings. Change the message font and the signature follows it.

How do you keep the signature’s own font?

1. Open Mail and choose Mail > Settings. Older versions of macOS label this Mail > Preferences.
2. Click Signatures, then pick your account in the left column.
3. Select your signature in the middle column. Its text appears on the right.
4. Untick Always match my default message font. Apple’s guide describes this option but does not show where it sits on screen. In community threads, users select the signature text first and find the option in that pane.
5. Select the text and set the font and size from the Format menu. Apple’s guide says the right column is where you change the signature’s formatting.
6. Under Choose Signature, make sure this signature is the default for the account.
7. Close settings, start a new message and check the signature in the compose window.
8. Send a real message to a Gmail address and an Outlook address, and check the copy that arrives.

When the signature still looks wrong for recipients

Some users report that a signature arrives larger than the body text. A March 2011 thread on Mac OS X 10.6.6 has 21 replies and describes a signature at 13.5 pt against 12 pt body text. A January 2016 thread on El Capitan has 13 replies and describes a signature that jumped from 9 pt to 16 pt and would not shrink.

Apple’s documentation does not cover these reports, and no reply in these threads is confirmed by Apple. Two things worth trying:

• Delete the signature and paste it again as a new one. In a September 2016 thread about font size changing while typing, the author reported that recreating the signature fixed it.
• Check the size of every line in the signature. One oversized line can make the whole block look wrong.

What the Mail font setting controls

A top answer in a December 2022 thread on macOS 13 says: “The settings in Mail preferences are only for the user-interface elements.” That is a community answer, not Apple documentation. It suggests that Fonts & Colors may change what you see while composing, not always what the recipient gets. Test with a real message before you trust either.

How Sendoff handles this

Sendoff writes font family and font size inline on the text elements of each signature, so the font and sizes are part of the HTML you copy. With Always match my default message font ticked, Mail uses your message font instead, which is why you untick it before you paste. Get a signature from the free email signature generator, then follow the Apple Mail install guide.

Sources

• Apple Support, Mail on Mac user guide, Change Signatures settings: https://support.apple.com/guide/mail/cpmlprefsig/mac
• Apple Community, “my mail font keeps changing to TIMES” (December 2022, macOS 13): https://discussions.apple.com/thread/254431761
• Apple Community, “Font size in email signature” (January 2016, El Capitan): https://discussions.apple.com/thread/7437648
• Apple Community, “Email signature is HUGE” (March 2011, Mac OS X 10.6.6): https://discussions.apple.com/thread/2779086
• Apple Community, “Apple Mail automatically changes font size while typing, Part 2” (September 2016): https://discussions.apple.com/thread/7689814