Many people decide whether to open an email or not, based on the subject line. An inefficient subject line would lead to low opening rates. MailChimp did some research on this, and discovered that: Words like "urgent" and "important" resulted in open rates that were much higher than normal. They found that these words, at the beginning of the subject line, led to higher opening rates: Urgent Breaking Important Alert This is also backed up by the research paper Influence tactics in virtual teams published in the Computers in Human Behavior journal, which states that the word Urgent "provides a quick jolt of pressure to get a target to realize the importance of a particular task" MailChimp also found that capitalization helps: While performing the analyses above, we looked at the impact of capitalization on open rates. The results were quite surprising. First of all, the use of an entirely capitalized subject line resulted in slightly higher open rates than usual for a given user/list. Surprisingly, they found that capitalizing only one word had a negative impact on opening rates! Probably not too new or surprising to anyone, but nice to see that there is a statistically significant difference made by these simple tweaks. I have not tried these out before, since I instinctively felt that it would look spammy (personally, I feel this thread title looks like spammy clickbait. What was your first reaction when you saw it?). I never did any testing myself though, and since MailChimp discovered the above based on 24 billion (!) emails, I think it is worth a try. You obviously shouldn't overdo it, as your email list would feel annoyed by getting "urgent" emails every other day. But if you frame the content correctly, it could be helpful when sending out last chance/limited time offers. Will you try out any of these subject line word tweaks with your list?