PwMailExt

Tips and Tricks / FAQ

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  • Support PwMailExt

Basic Operation (macOS version)

  1. Launch Mail.app.

  2. Click “Settings…” from the “Mail” menu to open it.

  3. From the tabs at the top of the window that opens, click Extensions.

  4. "PwMailExtensions" should be displayed in the list on the left side of the window, so check it.

    This completes the "Enable PwMailExt" process. Thank you.

Basic Operation (iOS version)

  1. Open the encrypted email sent with PwMailExt in Mail.app.
    If the email was sent using PwMailExt, it should have an attachment.

    (If sent using the iOS version of PwMailExt, the attachment file name will be "pwmailext.pwmailext")

    (If sent using the macOS version of PwMailExt, the text will be
    "If you do not know how to read this email,
     please ask the sender of this email.")

  2. Tap the attachment and tap Share from the pop-up menu that appears.

  3. Tap "PwMailExt" from the list of shared sheets that opens.

  4. You should now see a decrypted message.

    This completes the "Read encrypted emails sent with PwMailExt" process. Thank you.
If decryption fails
The recipient must be registered in advance in "encrypt destination conditions" in PwMailExt.
Otherwise, decryption will fail.

If decryption fails even though it has been registered in "encrypt destination conditions",
Please check again whether the email address conditions are correct and whether the password is correct.

If decryption still fails, please check with the sender to see if the email was sent in plain text.
The iOS version of PwMailExt does not support HTML emails. Also, only image files are supported as attachments.

Known problem

If you receive emails with titles like “Undelivered Mail Returned to Sender”
and messages containing text such as:
“Diagnostic-Code: smtp; 550 We are unable to send your email as one or more of
its attachments may be corrupted or may contain malicious content.”
This likely occurs because the encryption applied by PwMailExt
causes the email server to flag the message as spam, resulting in delivery/receipt being blocked.
As a countermeasure, use another email address and send/receive via a different mail server.

Since late October 2025, the above issue has been occurring on iCloud's mail servers.