Professional Emails: Security and Signatures

A professional email starts before you type a word: the address it comes from, how that domain is secured, and the signature at the bottom all shape how people read it. This post covers custom email domains and the protocols behind them, greetings and writing tools, signatures that display correctly in any client, and footer notices.

TLDR

Domain: use yourname@yourdomain.com, use TLS, prefer IMAP, and set up SPF, DKIM, and DMARC so no one can spoof you.
Writing: a simple “hi” works, and free tools catch clichés and grammar mistakes.
Signatures: plain text, default font and color, no images, full links, and your email address. See the example.
Footers: add a confidentiality or industry notice only if you routinely need one.

Domain name

yourname@customdomain.com

Custom domain names are more professional than a third-party provider like “@gmail.com.”

Configurations

Depending on how you implement the domain, there can be security concerns. For example, if you use a nonstandard email setup (i.e., configuring Thunderbird or using custom APIs to handle mail from your domain name), you may have configured insecure protocols during startup or followed tutorials that offer convenient but irresponsible advice.

Whichever provider you use, add three DNS records for your domain. SPF lists the servers allowed to send your mail, DKIM signs each message, and DMARC tells receiving servers what to do with mail that fails those checks. Without them, anyone can send email that claims to come from your domain, and your real messages are more likely to land in spam.

Protocols

There are three protocols commonly used for email: the Simple Mail Transfer Protocol (SMTP), the Post Office Protocol (POP), and the Internet Message Access Protocol (IMAP). All three use TCP. Message transfer agents—such as mail servers—use SMTP to send and receive email messages. Email clients (also known as “mail user agents” or MUAs) use POP and IMAP to read the messages in your mailbox.

Diagram of an email traveling from sender to recipient through mail servers — Simplistic diagram of how email works by The Impact of Email – Technical Aspects

SMTP

SMTP is the standard protocol for sending mail. Every message you send uses it, even from a browser, where your provider’s servers handle SMTP for you. If given the option, use TLS rather than SSL, which provides more security for SMTP.

POP and IMAP

Some institutions disable POP and IMAP by default. However, if you are interested in using a traditional desktop client (e.g., Outlook, Thunderbird, iPhone Mail), you will probably need to configure it. IMAP is usually the better choice. IMAP stores your emails on a server, while POP downloads them to your MUA. If your device is lost, you will have copies on a server if you use IMAP.

Too confusing?

Setting up custom email domains is difficult. If you are worried about navigating security effectively, I recommend holding off on setting up your email until you have time to seek guidance or figure it out.

Diagram of mail terminology: MUA, MSA, MTA, and MDA — Simplistic diagram of how email works. Source: Mail terminology by A Fresh Cloud.

To learn more about how email works, I recommend reading Mail terminology: MTA, MUA, MSA, MDA, SMTP, DKIM, SPF, DMARC by A Fresh Cloud; I used to link to the article, but the site appears to be down.

If you are interested in this topic, Glenn Messersmith writes about Hacking WordPress Emails and other fun WordPress features and misconfigurations.

Formatting, grammar, and wording

Greetings

Greetings are a great way to personalize emails, so I feel like this is the sender’s choice. I use “hi” in all circumstances, but there are other options. In written letters, I may use “dear,” but that is it.

Writing resources

Name	Usage
Cliche Finder	Finds cliche phrases in writing
Copyscape	Plagiarism checker. It does not always work well, but it is the only free and reliable plagiarism checker I’ve found.
Grammarly	Grammar checker
Hemingway Editor	Similar to Grammarly; the basic web editor is free.

Signatures

Many folks value formal and accessible email signatures. Formal email signatures match the font style, size, and color of the rest of the email. They also include a formal closing like “sincerely,” or “regards.”

Accessible signatures are compatible regardless of client. Unfortunately, many email clients can’t process signatures with icons, photos, and embedded links. As a result, text-based signatures with standard fonts, indenting, and coloring work best.

Additionally, I recommend including the email address in the footer because many email clients (e.g., Outlook) only show the sender’s display name; it’s even more common for email clients to do this when you forward emails. By including the email in the footer, it is easier for recipients and forward-ees to start an email with you regardless of client.

Concerns

Topic	Concern	Remedy
Text style inconsistent with the rest of the email	Looks strange	Use a default font
Custom colored font (e.g., orange or pink)	Themed email clients that incorrectly process the colored text, making it unreadable. Dark mode is a common example of where this happens.	Use default coloring; usually the default font color on your email client.
Images, icons, and links	Bad formatting on other email clients. This is extremely common.	Avoid images and icons. Include a full link that is also embedded. – (bad) http://www.oliviagallucci .com – (bad) website – (good) www.oliviagallucci.com Here, users can click your link if the client allows it. If it doesn’t, they can copy the text and paste it into their browser.
3rd-party designers	Embedding links or other information you don’t want in your email	Don’t use em!

Signature example

Format	Example
Closing, Name Pronouns Role Email Phone Preferred socials	Sincerely, Olivia A. Gallucci (She/Her/Hers) Double-BS Computing Security + Computer Science ’25 E: olivia[@]oliviagallucci.com P: 123 456 7890 Website: https://oliviagallucci.com/ LinkedIn: https://www.linkedin.com/in/olivia-gallucci Twitter: https://twitter.com/oliviagalluccii

Footers

Notices

If your brand routinely needs to provide disclosures and notices, that is a great thing to put under the signature of your email.

Confidentiality

Here is a standard confidentiality notice by the University of Hawaii:

CONFIDENTIALITY NOTICE: The contents of this email message and any attachments are intended solely for the addressee(s) and may contain confidential and/or privileged information and may be legally protected from disclosure. If you are not the intended recipient of this message or their agent, or if this message has been addressed to you in error, please immediately alert the sender by reply email and then delete this message and any attachments. If you are not the intended recipient, you are hereby notified that any use, dissemination, copying, or storage of this message or its attachments is strictly prohibited.

Occupation specific

Here is one Cyber Defense Magazine uses on its website:

FAIR USE NOTICE: Under the “fair use” act, another author may make limited use of the original author’s work without asking permission. Under 17 U.S. Code § 107, certain uses of copyrighted material “for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright.” As a matter of policy, fair use is based on the belief that the public is entitled to freely use portions of copyrighted materials for purposes of commentary and criticism. The fair use privilege is perhaps the most significant limitation on a copyright owner’s exclusive rights. Cyber Defense Media Group is a news reporting company, reporting job openings at no charge at our website Cyber Defense Professionals. All images and reporting of job openings are done exclusively under the Fair Use of the U.S. copyright act.

Post inspiration

This post was written for IGME 599, an Honors FOSS Independent Study (Summer 2022).

How to Write Professional Emails: Security, Signatures, and Branding