OpenPGP software
GnuPG is a free implementation of OpenPGP. It enables support for Apple Mail for Mac and Microsoft Outlook for desktop.
Mail clients
Thunderbird implements S/MIME and OpenPGP.
Apple Mail for both mobile and Mac and Microsoft Outlook for desktop support S/MIME without requiring additional software.
If you have an Apple device and want to verify that you are really messaging people that you intend, you can compare iMessage Contact Key verification codes in person or over the phone and manually approve it if the code matches.
This is my current iMessage Contact Key Verification code.
APKTID8lQ6pB3NbQFedSC2w76F5S_SBOC45uIhJ0kFXggpSW1c3Q
S/MIME certificate
Serial Number: 39 EE 6D EB 50 5C CC 35 CF 2B 41 AE 6A 19 54 46 10 7D 59 1C
Key Type: RSA
Expires: 2026-11-04 01:22:51 UTC
Key Size: 2048
Fingerprint: 3C BB B1 5A 25 AF BE D8 9C DC 35 7D 36 CD 10 39 77 24 F2 AC
Email Address: <jon [dot] teodoro [at] outlook[dot]com>
-----BEGIN CERTIFICATE-----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Q+xuy+VduubD+fK7vu6tayJ6aQ0BNzLQbtmD+LD2svFw/0MGkATaWvlYK4yC7rDs
XTSKaYnowfUzyq6usXXP8ucuuok5zrzPid7+H9HwICx9Y1qtQG/aow+a1kcECwM5
h30Y1YMmHvkI9GX1mC3VwkiX9rd4qDqwkFnBkoY7LEE9RkL8w7ma2TIFMR6MIRiW
y62w4HeXBJdpPloN3A6FBADh6R1sJTTDa4cdxxxF6mgtKHQ8tjBRwOlb321NEHo=
-----END CERTIFICATE-----
PGP key
Key ID: C9C41841
Key Type: EdDSA
Expires: 2027-05-07
Key Size: 255
Fingerprint: F510 BE7C 99CD 7790 821E 0E07 34D4 A80B C9C4 1841
UserID: Jon Teodoro <jon [dot] teodoro [at] outlook[dot]com>
-----BEGIN PGP PUBLIC KEY BLOCK-----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CQoLBRYCAwEAAAoJEDTUqAvJxBhBdrMA/2bor9HhOm5qIRJcf2v+W+/t4SxwBsyd
d5Unff7bpCPNAQCl2dRM+hIKupUjMm5ck/wy00L5JXFGWIX2PtrcT4SqCYiPBBMW
CAA3FiEE9RC+fJnNd5CCHg4HNNSoC8nEGEEFAmgawc8CGwMECwkIBwUVCAkKCwUW
AgMBAAUJBbdwhgAKCRA01KgLycQYQefWAP0UjFORQBjoSeBhermAfacZlpvnWcWL
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AmrHRWwFCQeYpAYACgkQNNSoC8nEGEFXUAD/QuuWettAYSah7w0ct304pXCqvOkM
BzKklESQj2l1f4EA/0DycNmaU/rEwOvnh1FQqmW/qPsbiiR2hbCeYJ69PpsMuDgE
ZEPY2hIKKwYBBAGXVQEFAQEHQPwgJ7z6MkKQy8tUnCrXAQfzYPaMhA3/VNjcJ5ah
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CQOxUwYACgkQNNSoC8nEGEHRGQD+I2rpF/ISnZQE9eWhojcCLzeqAr7Yk0FJbveZ
XFeGKGEBAIa+hg/srMzM22kXfJ6kB5+CAHtRsVt++rsOOqXbOskHiH4EGBYIACYC
GwwWIQT1EL58mc13kIIeDgc01KgLycQYQQUCasdGSwUJCGSg4gAKCRA01KgLycQY
QYN9AQC3DEbkOiX5EOnBcfz0rrNL45SOvlg9f8iSyeSEu+8w/QEA9OJ3l8wh956e
s7EShTZ8884P3Z3/D8+Z4dGxKQ4eWQA=
=hwVF
-----END PGP PUBLIC KEY BLOCK-----