The minimum for a cold message is your name, your business name, a phone number, a valid physical postal address, and a clear way to opt out. The postal address is the element almost universally missing, and its absence is the most common breach of the rules governing commercial email in the United States.
The opt out line does not need to be elaborate. A sentence saying to reply with no thanks and you will not contact them again is sufficient, provided you actually honour it. A working unsubscribe link achieves the same and is more appropriate at any volume.
Keep it short despite adding those elements. Four or five lines total. A cold message under one hundred and fifty words followed by a twelve line signature is unbalanced, and the signature is not the part anybody reads.
Leave out the things that decorate rather than inform. Logos and images raise the probability of filtering and frequently fail to load. Inspirational quotes, environmental notices about printing, and lengthy legal disclaimers add length without adding anything a recipient uses. Social icons are rarely relevant in a first approach.
Be careful with tracking. Read receipts and tracking pixels are widely detectable, increasingly blocked, and regarded poorly by recipients who notice. On a first message to somebody who does not know you, the risk of appearing to surveil them outweighs the value of knowing whether it was opened.
A single link is acceptable and two is usually too many. Your website is enough. Multiple links, particularly shortened ones, are a pattern filters associate with bulk sending, and they dilute whatever action you actually wanted.
Make the phone number real and answered. A cold email that produces a call is the best outcome available, and a number that rings out undoes the whole exercise. Where you cannot answer reliably, say when you can.
Set it as a default in your mail client rather than adding it manually, because the elements that matter legally are exactly the ones you will forget under time pressure. Once configured you never think about it again.
Then consider using a slightly different signature for cold outreach than for ordinary correspondence, with the postal address and opt out present in the first and unnecessary in the second. Most mail clients support multiple signatures and switching takes a moment.
Test it on a phone before adopting it, because a signature that wraps awkwardly on a narrow screen is the version most recipients will see.
Review it whenever your details change, particularly the postal address. A signature carrying an address you left two years ago fails the requirement it exists to satisfy.
Keep the same signature on follow up messages rather than shortening it, since each message in a commercial exchange carries the same obligations as the first.
Include your role where it clarifies who you are, and omit it where it does not. Owner or founder tells somebody they are speaking to a decision maker, which shortens the exchange.
Avoid confidentiality notices on cold email entirely. They have no effect on an unsolicited message to a stranger and they read as though copied from somewhere else.
Match the tone of the signature to the message. A formal block under a short conversational note reads as though two different people wrote them.
Keep a plain text version available, since some recipients and some systems strip formatting entirely and the details still need to survive.
Check it renders correctly in the clients your recipients actually use rather than only in your own.