Authentication and infrastructure
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How does email forwarding affect authentication results?
The Domain-Based Message Authentication, Reporting, and Conformance (DMARC) authentication standa...
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What is an open relay and how do I close one?
An open relay is an improperly configured Simple Transfer Mail Protocol (SMTP) server allowing th...
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What is an open proxy and how do I configure my servers to avoid it?
An open proxy is a server that acts as a "middle-man" for requests from one server or network to ...
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What is the difference between the Mail From (MFrom) address and the From address?
The key differences between the Mail From (MFrom) address and the From address include: The send...
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Do SMTP servers reject email if the rDNS does not match the HELO?
Some Simple Mail Transfer Protocol (SMTP) servers are configured to reject your email if the reve...
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How long does a Domain Name System (DNS) change need to take effect?
Domain Name System (DNS) changes typically take up to 24 hours to take effect. It is the projecte...
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How to implement the List-Unsubscribe header
List-unsubscribe resources RFC 2369 RFC 8058 Follow the steps below to implement the List-Unsub...
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What are some examples of Mail Transfer Agents (MTAs)?
There are many different options for Mail Transfer Agent (MTA) software. Some of the more widely ...
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Can email be sent from IPv6 IP addresses?
Yes, email can be sent from IPv6 IP addresses. Your email server, or Mail Transfer Agent (MTA), ...
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Does Transport Layer Security (TLS) improve deliverability?
At this time, there is no proof that Transport Layer Security (TLS) improves deliverability. Howe...
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What are the different types of DMARC policies?
There are three different types of Domain-based Message Authentication Reporting and Conformance ...
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How many IPv6 IP addresses are there?
IPv6 uses a 128-bit address which allows for 2128 , or approximately 3.4 x 1038 addresses. 3.4 x ...
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What do I need to know about sending from shared and dedicated IPs?
An important decision you have to make as an email marketer is whether to send your email from de...
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What is the d= field in DomainKeys Identified Mail (DKIM)?
The d= field in DomainKeys Identified Mail (DKIM) is the domain of the entity signing the email m...
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What is FCrDNS and what are the requirements?
Forward Confirmed Reverse DNS (FCrDNS) is a DNS technical configuration that shows a relationship...
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Should I continue to use DomainKeys?
When DomainKeys Identified Mail (DKIM) was put into practice, it made the use of DomainKeys obsol...
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What factors influence how many IP addresses I need for my email marketing program?
Determining how many IP addresses your email marketing program needs can be difficult. Whether or...
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How do I make sure my host names clearly identify my sending identity?
Sender host names must clearly identify their sending identity. When scaling your Mail Transfer A...
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What are the rules for email address syntax?
For an email to be delivered, it must have a valid address that follows certain rules of syntax. ...