Anti-spoofing for Custom Domains (SPF, DKIM & DMARC)

You can always just check the DNS Records yourself.

Short anwer: Yes, mailbox.org uses SPF, DKIM and DMARC.

Long answer: Everyone can send Emails in your name anyway. The mailbox.org SMTP servers do not check if you spoof your from address. See this discussion in the german forum: https://userforum.mailbox.org/topic/mailbox-org-smtp-server-stellt-mails-mit-gefakten-absender-zu

Gmail antispam system uses DKIM and DMARC. If I send an email with my custom domain to a Gmail user that will may be redireced to spam

The easy way is to use openssl and generate your private and public keys with this:

1. openssl genrsa -out private.key 1024
2. openssl rsa -in private.key -pubout -out public.key

If you want a 2048 bit key change "1024" with "2048".

With a TXT record you have to add:

• dkim._domainkey.yourdomain.TLD as a host name (change "dkim" with everything you want e.g. "default, key1" etc).
• in the value part v=DKIM1; k=rsa; p=your/generated/key

The SPF it's easy and reported in the support section of mailbox.org site, just add in a TXT record: v=spf1 include:mailbox.org and leave the host empty.

DMARC it's just a string, you don't have to generate nothing, again in a TXT record put:

• _dmarc in the host part
• v=DMARC1; p=none; rua=mailto:youraddress@yourdomain.TLD

(You can create an alias just for DMARC like reports-dmarc@yourdmain.TLD)

You can find openssl for every GNU/Linux distro and also on Windows I think.

Hope this helps you.

I'm happy to say that the mailbox.org team added DKIM and DMARC support.

In the knowledge base there are all the info. You can check it here https://kb.mailbox.org/display/MBOKBEN/Using+e-mail+addresses+of+your+domain

There's a detailed explanation of how to add DKIM with your domain.

Hope that is helpful.