The glance
Test your subject line.
A subject line gets a glance on a lock screen, not a reading. This tester scores yours against the rules our 4,000,000-send corpus taught us, and names exactly what to cut.
Questions
The details.
How long should a cold email subject line be?
Three to five words, under about 45 characters. Phone lock screens and inbox lists truncate the rest, and the truncated half is where most people put the point. Short survives; clever gets cut mid-
Do personalised subject lines work?
A resolved merge field \u2014 the prospect's company, a competitor, a number \u2014 outperforms cleverness. An unresolved one produces \u201cHi ,\u201d which is unrecoverable. The rule: personalise from the lead file, verify the field fills, never personalise from memory.
Why is a fake Re: so bad?
It buys one open at the cost of everything after it. The reader knows there was no prior thread; filters recognise the pattern too. It is the single most trust-destroying character sequence in cold email.