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SPF and DKIM are two message authentication methods that can be used to show spam filters that the sender's email address appearing on your messages is in fact valid, and that this address is not 'spoofed'. By providing spam filters with a way to authenticate that your messages are not spoofed, your messages will have a greater chance of making it to the recipient's inbox, as opposed to being trapped by the recipient's spam filter.

We recommend that you setup an SPF record for the domain associated with the email address from which you send email, following the instructions below, to show that mail sent from this address through UltraSMTP's servers is legitimate. By default, UltraSMTP signs every message sent through the service with a DKIM signature using our DKIM signing keys, or optionally yours (see below).

Setting up SPF and/or DKIM involves creating a DNS record for the domain name associated with the email address that you send mail from. If you do not have control of the domain name associated with your email address (for example, if you send mail from a @gmail.com or @yahoo.com address), then unfortunately you will not be able to setup SPF or DKIM. However, if you send mail from an address @yourcompany.com, and you have access to create DNS records for yourcompany.com, then you will be able to setup SPF and/or DKIM for yourcompany.com. If you are unfamiliar with the process for creating DNS records, you will need to consult your DNS provider for help.

SPF
If you do not already have an SPF record for your domain, create a new TXT record for your domain containing the following:
v=spf1 include:ultrasmtp.com ~all

This shows that mail sent from a sender's address in your domain is authorized to be sent from an SMTP server in UltraSMTP's network.

If you already have an SPF record for your domain, or if mail sent from senders' addresses in your domain is sent through other SMTP servers in addition to UltraSMTP's SMTP servers, include the following directive in your SPF record:
include:ultrasmtp.com

This shows that mail sent from a sender's address in your domain is authorized to be sent from an SMTP server in UltraSMTP's network (as well as any other SMTP servers that might be included in the SPF record).

DKIM
By default, UltraSMTP signs all outgoing messages with a DKIM signature using signing keys associated with our domain, ultrasmtp.com. By doing so, we are vouching on your behalf that messages that you send through UltraSMTP are legitimate. However, some spam filters are known to place more trust in a DKIM signature that was signed using keys associated with the sender's domain, instead of a third party's domain. For clients that prefer to have their messages DKIM-signed using keys associated with their domain, we have the ability to do so. Contact us, and we will create a DKIM key-pair to use for signing your messages, and send you the public key to include in the DNS for your domain, along with instructions for doing so.


Related:
Message Authentication

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