Thank you everyone for your follow up.

Your suggestion, Jarland, is very interesting. I also find it odd to have
the sakura.ne.jp server appear out of nowhere!
If it were to be a hack of my account, it would be Mailgun->Gmail, that's
all. (well, I hope so)

... and, you put me on the right track!
I found the reason, but I think I need to contact Mailgun first as it seems
to be a very bad security issue...

I'll keep you posted, but I know how they did it.

I'll definitely keep you posted as soon as I have news from Mailgun.


Le mer. 11 janv. 2023 à 22:52, Mark Alley via mailop <[email protected]> a
écrit :

> Looking at it again, I agree with Todd and Jarland's hypothesis;
> Forwarding sounds more plausible than an API submission via compromised
> credentials in this case. I think that hit the nail on the head. This also
> correlates to one of Mailgun's product offerings
> <https://www.mailgun.com/blog/product/intelligent-email-forwarding-with-mailgun/>
> for forwarding which fits the bill.
> On 1/11/2023 3:29 PM, Todd Herr via mailop wrote:
>
> This looks like a message that maybe might've been sent to a reflectiv.net
> address (perhaps the one advertised on your website? contact at
> reflectiv.net?) and then automatically forwarded by Mailgun (which hosts
> inbound mail for reflectiv.net) to a Google account (since Mailgun
> probably doesn't do mailbox hosting).
>
> That's just purely a guess, based on
>
>
>    1. X-Mailgun-Incoming: Yes
>
> appearing in the headers, and the MX record for reflectiv.net, and the
> message coming to Google with the following Return-Path:
>
>    1. Return-Path: <bounce+3dbf11.71c471-{redacted}=
>    [email protected]>
>
> Does that sound plausible?
>
> On Wed, Jan 11, 2023 at 4:07 PM Cyril - ImprovMX via mailop <
> [email protected]> wrote:
>
>> Hi everyone!
>>
>> Today, I received a spam ("I got full access to your computer and
>> installed a trojan" kind of email). In general, I completely ignore these,
>> but today was different:
>>
>> The sender and recipient were my own email! What's odd is that I did
>> configure SPF (granted, with a "~") but also a DMARC reject policy.
>>
>> Looking at the email headers and also the output from GMail, both SPF and
>> DKIM were successful ("pass"), which means the sender, somehow, was able to
>> send an email using my account.
>>
>> I would love your input on the issue, but here are my thoughts so far:
>>
>> 1. My account was compromised, and the password was leaked, allowing that
>> user to send an email with my account. This would make sense, but the
>> sending account was only used to be configured within GMail. As soon as the
>> password was generated, I pasted it on GMail and never saved it elsewhere.
>> 2. Theoretically, if I were to create an account on Mailgun, I would be
>> able to send an email from my account and have a valid SPF for any other
>> services that use Mailgun too (since their SPF would include Mailgun's
>> IPs), but it wouldn't explain the valid DKIM though. For this, Mailgun
>> should only allow my account to be able to send using my domain.
>> 3. Did Mailgun have any database leak that I wasn't aware of?
>>
>> Of course, as soon as I saw this email, I generated a new password for my
>> account, but I still wonder how this could have happened. I would
>> appreciate if you had any insights I've missed that would make sense.
>>
>> Here are the headers from the email with my end email redacted:
>> https://pastebin.com/knqbTa8K
>>
>> Thank you!
>> _______________________________________________
>> mailop mailing list
>> [email protected]
>> https://list.mailop.org/listinfo/mailop
>>
>
>
> --
> *Todd Herr * | Technical Director, Standards and Ecosystem
> *e:* [email protected]
> *m:* 703.220.4153
>
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