What CASL requires#
CASL requires express or implied consent before sending and identification of the sender in every message.
What email subject lines are#
The subject line and preheader are the two text fields shown in the inbox list before a message is opened. They determine whether a recipient opens, ignores, or reports the message.
Why it matters#
Subject lines are the highest-leverage copy you write. They also affect complaint rates, which feed reputation.
How email subject lines supports CASL compliance#
Regulators and recipients need to identify who sent a message and trust that opt-out mechanisms work. Email subject lines contributes by subject lines are the highest-leverage copy you write. They also affect complaint rates, which feed reputation.
Implementation steps#
- Keep subject lines under 50 characters so they survive mobile truncation.
- Write the preheader as a continuation, not a repeat of the subject.
- A/B test one variable at a time with a statistically meaningful sample.
- Avoid deceptive 'Re:' or 'Fwd:' prefixes, which violate CAN-SPAM and raise complaints.
Frequently asked questions#
Do emojis in subject lines hurt deliverability?
Not directly. They can hurt engagement with B2B audiences and render inconsistently across clients.