What is an email address?
An email address identifies a mailbox or routing destination, usually in the form local-part@domain. The part before the at sign is interpreted by the mail provider; the domain after it is resolved through DNS. An address can be valid in form yet fail to receive mail if its domain or mailbox is not configured.
Parts of an address
The local part can include letters, digits and certain punctuation, but providers apply their own restrictions. Some systems treat upper- and lower-case local parts differently in theory, while most consumer services do not. Do not assume that dots or plus signs are ignored: that behaviour belongs to a particular provider, not to all email addresses. The domain may include internationalised characters, which are encoded for DNS use.
A display name such as “Support Team” is separate from the actual address. Before replying or sending sensitive information, inspect the address itself. Similar-looking letters and domains can mislead a reader even when the visible name seems familiar.
How a message is delivered
A sending mail server looks up MX records for the recipient domain and attempts delivery to a suitable receiving server. An MX target normally resolves to an address through its own A or AAAA record. The receiving service then decides whether the mailbox or alias exists and whether to accept the message. DNS alone cannot confirm that a particular person controls the address.
Delivery can fail because the domain has no usable mail configuration, the mailbox is full, filtering rejects the message, or the receiving server is unavailable. A successful send action in an app only means the app handed the message to its server; it does not guarantee delivery to the recipient’s inbox. Keep the returned error or bounce notice for diagnosis.
Aliases and account security
An alias forwards or routes mail to another mailbox, while a disposable address may expire after a short period. Neither automatically makes the sender anonymous: providers and messages may retain identifying data. Use separate aliases when you need to manage subscriptions, but check whether the service supports receiving verification replies and password resets.
Protect the main mailbox with a unique password and multifactor authentication where available. Recovery access matters because many other accounts depend on email. Be cautious with unexpected attachments and links, and verify requests for credentials through a known channel. Mail authentication records such as SPF, DKIM and DMARC help domains express and check sending policy, but do not make every message trustworthy.
Checking an address
Check spelling, especially the domain, before sending. A syntax check cannot prove a mailbox exists, and intrusive “verification” services may reveal the address to third parties. For a business domain, inspect its MX and related DNS records and send a test message through the normal mail service. If delivery fails, use the bounce code and provider logs to narrow the cause.