I'm using macOS Catalina (10.15.3), but this problem exists at least 5 years in the built-in mail application (Mail.app).

The Problem

Mail.app in macOS seems display some incoming mails' fonts way smaller than they are supposed to be shown. In any other mail client on Windows, those mails look totally normal and the font size is well readable. Usually, it applies to personal emails formatted in RichText or HTML, that don't have particularly styled text other than some bold or colored text. It does not apply to newsletters and most generated email from online shops etc.

font on mail body in really small


  1. One way to cope with this problem is to repeatedly press CTRL-+to increase the font size. But, as soon as you change to a different email, the size is reset to the default (which in turn is the correct behavior). When opening the same email again, you have to increase the font size all over again. It is mentioned in Mail from AOL, font to small Fix? (5 year old question with no real answer).
  2. You can increase the overall font size for emails in settings (Fonts & Colors > Font for email). However, this will also increase the font size of subject, headers and some other text that is displayed in the preview pane for all emails, and it just looks aweful. Font set to Arial 18

  3. (Not tested) It might be possible to apply an AppleScript that modifies the email content. It is mentioned in Replace font in incoming mail [mail.app]. I can't even think that it will be successful. It might be a huge security issue.

NOT working (or no longer)

Possible Reason

When looking at the source of this problematic emails, I can see a lot of <font> tags, especially parts like this, where the size="2" might be the issue:

<font size="2">Ich danke dir!<br></font>

It used to be possible to (kind of ) fix this by editing /Applications/Mail.app/Contents/Resources/Message.css. This file no longer exists.

Some References to this Problem on other Sites

This problem seems to exists for years and has not been addressed properly by Apple. For me, it still is the most frustrating problem after switching to the Mac from a Windows PC. Any help is appreciated!

  • The really small font in some emails is determined by the sender and whatever email client they use and what they set their fonts and size to. There used to be an option to show the pain text alternative but that seems to be missing in my version (Mojave) of mail.app, too bad. – Steve Chambers Mar 30 '20 at 1:11
  • I'd say this is more general ... I've had the same issue in Outlook 2016 for mac for a while now. It only ever seems to happen with mail sent as plain text. – compuphys Mar 30 '20 at 9:30
  • It definitely happens with HTML emails, but not with plain text. The latter look great and have a separate font setting. – Fabian Mar 30 '20 at 22:22

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