I'm using PHP mail() to send an email from my server to two different accounts, one which is my Gmail account, which SPF passes with, and one to an account hosted by my domain provider, which is then forwarded to my Gmail account. That causes SPF to fail because the originating IP is different.
But, there's no way to tell if the email address you send emails to is the recipient, or forwards them elsewhere. So is there any way to allow SPF to pass through any (unknown) relay?
It's unclear exactly what you mean here. Are you using arbitrary From addresses?
Generally, SPF control over email sources is handled in a few different ways:
Authorise your domain provider's servers to send from your domain (i.e. add them to your SPF record)
Hope that your hosting provider's mail servers support SRS, the Sender Rewriting Scheme, which they should
Allow any IP to be a source of email for your domain by adding +all to your SPF record (clearly a bad idea!)
Related
I have multiple domains pointing at nameservers of a shared hosting platform and manage all the emails of these domains using just one address called hello#domain-a.com as an example.
Because all of these domains work under one business and I don't want to manage multiple accounts, this address also receives all the emails for my other domains domain-b.com and domain-c.com using forwarders.
Sometimes I still need to change the From address, which is why I set up identities in Thunderbird using domain-a.com as the host with hello#domain-b.com and hello#domain-c.com as the From addresses. While doing that, I realized that I didn't need to create these accounts on the mail server and all emails that were sent by either hello#domain-b.com or hello#domain-c.com had a PASS on both SPF and DKIM.
This made me wonder, whether someone else on the same shared hosting platform (whois checkup shows there are more than 600 other domains) could also just use any of my domains to send emails and would get a PASS on both SPF and DKIM, basically making it useless in that specific scenario.
Can anyone on the same shared hosting send emails using my domain with a PASS on both SPF and DKIM?
Why is it possible to use domain-a.com as the host and hello#domain-b.com or hello#domain-c.com as From addresses and still send messages that way? The test messages I have sent using that method don't show domain-a.com but the domain of the From address in their headers. Is this normal behavior? Since I didn't set up any individual accounts for domain-b.com and domain-c.com, I honestly didn't expect this to work.
Thanks in advance.
If someone is on the same shared host as you, they will likely have the same IP address, and so if your SPF includes that IP, they will indeed be allowed to send messages from your domain. The simple solution to that by itself is don't do that – don't put critical content on shared hosting.
The next step is DKIM. DKIM has nothing to do with IP addresses, and sending from a shared host will have no effect, so this is your best defence against this kind of spoofing. A DKIM signature is signed by your private key (which nobody else should be able to access, even on shared hosting – though it is far more at risk there than on your own server). Because they can't see your key, they can't produce DKIM signatures for your domain, and thus messages they try to send from your domain will not contain a valid DKIM signature and they will not be able to get a DKIM pass result.
It could be that your hosting provider is also adding a DKIM signature of their own as an intermediary, though it will match their domain, not yours. You can add your own as well as messages can contain more than one DKIM signature.
To force alignment of From address with the envelope sender (which ends up in a return-path header at the receiver), you need to look at DMARC, specifically the adkim and aspf parameters.
Another approach would be to not send mail through your hosting provider but via some other mail server. This would let you have an SPF record that does not include your hosting provider's IPs. You may find however that you can't do this because low-end hosts tend to block outbound SMTP.
If I have a domain example.com that is using gsuite (DNS settings at registrar has gmail cnames, spf & txt records etc) and I have another service sending on behalf of the domain (Klaviyo). Do the gmail DKIM and DMARC settings help to strengthen the deliverability of those emails sent by the other service (Klaviyo)?
To answer your question: A DMARC reject or quarantine policy helps improve deliverability for all parties that send on behalf of your domain AND properly authenticate by SPF or DKIM, in alignment with your domain.
DKIM consists of a cryptographic key pair. You publish the public key on the Internet and you use the private key to sign headers of your outbound emails. This signing is done on the sending server. So unless Klaviyo is using Google servers to relay your messages, those messages are not being DKIM signed by Google.
You should follow the instructions provided by Klaviyo here, so that the emails you send from their platform, using your email domain, will authenticate properly and will NOT fail DMARC.
Update:
Say you own the domain myexample.com, then you should publish a TXT record at the root of that domain that looks like "v=spf1 include:_spf.google.com ~all". Additionally you can add any other services or servers to this record as you see fit. You don't need to add Klaviyo to your SPF record as they will try to authenticate from the send.myexample.com domain used in the bounce address. That is what you created the first CNAME for. It redirects to an SPF (and MX) record hosted at Sendgrid. Additionally, Klaviyo will authenticate those emails using DKIM.
In order to make DMARC work, you need to publish another TXT record at _dmarc.myexample.com, if you haven't already, looking like: "v=DMARC1;p=none;rua=mailto:DMARC#myexample.com;". Then you'll start receiving aggregate reports at the mailbox you supplied. Once you're confident you've included all required parties in your authentication scheme, you can move to a p=reject policy in order to protect your domain.
Yes, DKIM and DMARC settings do help deliverability.
I assume that Klaviyo does what my company Autoklose is doing as well, and that's using Gmail API to send the email in your name. That means that they only indirectly affect the sending process and the email itself is sent from Google servers and not Klaviyo's servers.
Also, you have to be aware that DKIM & DMARC are only two of the factors in successfully delivering your email. For example, having DKIM & DMARC correctly set gets you positive points but if your domain is blacklisted, it still might not get delivered.
I have an email address forwarding to a gmail account. I then use SMTP to send a response from gmail via the domains SMTP server. This is all set up fine. However some recipients are not receiving the emails? Is there further configuration I need to do on the domain side?
I am told I need to configure the SPF, DKIM and DMARC records but I have no idea what the configuration/values should be?
Having SPF, DKIM and DMARC set up is seldom a prerequisite for having your email delivered. If your email domain and servers have a decent reputation, you won't, generally, run into to much trouble.
However, it is best practice to set up all three, to start authenticating your emails and making it harder for others to impersonate your email domain without authorization. I'll outline the basics for you:
Why Authenticate
Phishing: Email Authentication will make it harder to impersonate your email
domain, without authorization. It (somewhat) protects your colleagues, partners and customers against phishing.
Brand Reputation Protection: Phishing from your domain can harm the reputation of your brand.
Deliverability: Authentication improves deliverability because it's weighed heavily in determining whether or not the email is legit.
DMARC
DMARC will try to find successful authentication for servers sending on your behalf. Specifically, it will look for a Pass on SPF or DKIM, in alignment with the email address (domain) that is being showed to the recipient in his email client. This is known as the Header.From field. (Not to be mistaken with the Sender field, the Reply-To field or Return-Path).
SPF
SPF is basically a list of IP addresses, published as a TXT DNS resource record, listing all servers that are authorized to send email for the domain the record lives in. This does not include subdomains, those require additional SPF records. One of the (many) problems with SPF: Receiving servers need to check the Return-Path email address to lookup the SPF record, instead of the Header.From domain. There is no need for the Header.From email address and the Return-Path address to share any of the domain part, according to the SMTP RFC. Thus where DMARC comes in.
DKIM
Signing an email message with a DKIM private key, requires you to publish a matching public key in the subdomain _domainkey for the domain your signing for. The receiving server will look for d= value and the s= value in the DKIM signature to construct the correct DNS TXT resource record to query, holding the public key. Example d=stackexchange.email s=s1 will result in a DNS query for the TXT record s1._domainkey.stackexchange.email. The same applies here as with SPF: The d= value does not have to match with the domain portion of the Header.From email address.
Unfortunately the configuration and values are very specific, depending on which parties are allowed to send on behalf of your domains, the subdomains you use and how you use them, etc. Especially SPF has a few limits that will make the setup harder.
I have question concerning SPF records.
The website (eg www.example.com) of one of my clients has a contact form that sends mails to contact#example.com.
We only provide the hosting of the website so we do not manage email accounts, DNS records, etc .. only webspace. So my clients manages the DNS settings, nameservers, mail servers, etc..
The mails are sent using PHP but they are never received by contact#example.com
When I change contact#example.com to an email address outside the domein eg contact#test.com, I do receive the contact email.
My conclusion is that their mailserver blocks mails from our IP address because PHP sends mails to an email address that has the same domain but has another IP.
Also, my client uses Google Apps for email so the MX records on their DNS server point to Google.
How can I fix this issue? Does my client need to add an SPF record that accepts our IP address? If so, whats the correct SPF syntax for this?
If your the domain has SPF records defined then you need to add the address of the web server to the SPF records.
You can check the SPF records of the domain on this website: http://spf.myisp.ch
The best way would be to check the log files on the web server or on the server of the receiver to find out what the problem is.
Make sure cpanel does not have any MX records since you are not hosting the dns
From the definition of SPF, SPF only authorizes IP address. For one of our domain name, we have created an SPF record to allow only A and MX IPs as genuine sender. This domain is hosted in a shared-hosting environment along with many other customers.
In such setup, owners of other domains on same host can spoof my emails easily. Is there any way SPF still work?
(correct me if my understanding abt SPF is wrong)
Yes they can spoof them but it would be very very unlikly.
If you are concerned about your personal mails that you send out or automatic mails from any system you provide on said host, you might consider signing them cryptographicaly to enable recipients to check if they are genuine.
I think there techniquies implemented in some mailservers to sign mails automaticly AND there is of course DNS signatures but what the status there is is bejond my knowledge.