Variable testing is a process of testing different elements in an email message to see which ones produce the best results. For example, you might test different subject lines, images,…

The email subject line is the brief heading that appears in the email’s inbox, telling the recipient what the email is about. A good subject line should be clear and…

A spam filter is a program that is used to identify email messages that are considered to be spam. These email messages are typically sent in bulk and contain content…

A soft bounce is an email message that gets returned to the sender because the recipient’s email server is temporarily unavailable. A soft bounce might occur if the recipient’s email…

The Simple Mail Transfer Protocol (SMTP) is a communication protocol for electronic mail transmission. As an Internet standard, SMTP was first defined in 1982 by RFC 821, and updated in…

Sender reputation is determined by a number of factors, but email service providers (ESPs) primarily consider the complaint rate when making deliverability decisions. Complaint rate is the number of people…