"Unable to verify message signature" message pops up when I try to send emails

I believe I have found the answer to this issue.

In the message compose window, on the far right end of the Subject line, there are two icons. If you click the icon on the right to uncheck it, you will stop digital signing in the message and your message recipients will stop seeing the warning.

I spent hours researching this and deleted and recreated the mail account in Mail several times without success.

I found the answer on this page on the MIT website: Q: Apple Mail - unable to verify message signature

Hope this answers for others.

Hello JJSter,

Thank you for keeping us updated on your results. It looks like we did share the following resource on how to trust a certificate: Trust a certificate on Mac - Apple Support

If those steps didn't help you, you can try to remove the affected email account and re-add it back to further isolate this issue you're experiencing. Remember to please any emails you have pending prior to attempting this step: If you can’t send or receive email on your Mac - Apple Support

1. Remove your email account in Mail.

2. Add your email account in Mail again. When adding the account, make sure that you choose the correct email service provider for your email address.

3. Try to send and receive email.

We hope this step helps you. Thank you for using Apple Support Communities. Take care.

I ended up calling apple support and sharing my screen, and the helper found a teeny tiny checkbox on the signature dialog box that we ticked and it solved the problem. Sorry I cannot be more specific, but either call Apple or scour every dialog box you find for a 2-pixel-sized checkbox that says to trust the signature or whatever.

Hi there JJSter,

We're happy to provide some information. It's likely an issue with certificates or the email address you're sending from.

If the Mail app  on your Mac shows a banner stating that it can’t verify a signed message, it might be due to one of several reasons.

* The message may have been changed after it was sent. Ask the sender to resend it.

* The sender’s certificate may have expired. Ask the sender to renew the certificate and resend the message.

* You need to trust the sender’s certificate.

* The email address on the S/MIME certificate doesn’t match the From address. The sender needs to change the From address so that it exactly matches what is used on the sender’s S/MIME certificate.

You'll find this information here: If Mail on your Mac can’t verify a signed email - Apple Support

With that said, follow the steps I the link above to 'Show Details' and get a better explanation of why this is happening and what you can do to resolve it.

Also, the steps in this support article may be helpful: If you can’t send emails in Mail on Mac - Apple Support

Take care.

Even though the window goes blank and it gives an impression that all is lost, you can Save and all will appear in the Drafts. Still very annoying!

"It is my email whose signature cannot be verified when I go to send something. No problems with incoming emails. How to fix this issue please. "

Mine is even stranger:

• this only started when I upgraded from High Sierra to Monterey and the native Mac Mail client that comes with those OS versions
• If after that dialog box shows up I just dismiss it and re-send it almost always goes through the second time and ALWAYS goes through on the third try.

In the same boat. I have been using Apple mail for decades with no issues, but recent updates have caused this problem. I have done all the suggestions below and they don't help.

This issue has caused me to loose many emails and occurs at random times.

Please fix this Apple as I would really love to not have to find a new mail program.

Still no solution.

Still losing emails because of this.

It has nothing to do with trusting incoming emails and their sender, at random times it is not trusting my own emails and causes me to lose long typed out emails.

Whats the deal Apple? Please address this issue!!

Same problem here. 90% of emails are fine. 10% are not. Show as sent, no bounce back, but recipient never receives. And no way to know which is which. So I only randomly discover that some recipients never got the email. Affected emails all show (after send) as "Unable to verify message signature."

Anyone else using WiseStamp or similar automatic email signature? I'm wondering if this might be part of the puzzle?

Hello, the post above seems oriented to incoming mail. The issue is for outgoing mail.

Similarly to what unclemioltie states "If after that dialog box shows up I just dismiss it and re-send it almost always goes through the second time and ALWAYS goes through on the third try."

Except that when this occurs, the mail does not send when I try to again - I need to cancel it, save as draft and resend - it then ALWAYS sends successfully.

I have deleted and recreated the mail (gmail). This did not resolve this issue. This ONLY occurs with email. None of my other (4) mail accounts in Mail have any issue.

Why is MY outgoing mail failing on MY trust certificate failing on MY laptop, where I have full rights??? this makes no sense!

My guess is that the problem is somewhere else and "signature verification failure" is just some random error reporting that has nothing to do with the problem. My friends have started migrating to Outlook. I am about to do the same since it seems that Apple has no interest in fixing this.

It is my email whose signature cannot be verified when I go to send something. No problems with incoming emails. How to fix this issue please.

I'm having the same problem. I'm not very tech savvy in these matters...I downloaded all the DER certificates but they all have a red x next to them in keychain. Please help.

Exact same problem, and the posted solutions are not germane to our situation. Please help!