An email client is software that lets you read and write email by connecting to one or more mailboxes. Desktop and mobile examples include Outlook, Thunderbird and Apple Mail; the technical term is MUA.
Why it matters
A client needs the right server settings to work: an incoming server using IMAP or POP3 and an outgoing server using SMTP, each with a port, encryption method and credentials. Many providers also use modern sign-in (OAuth) instead of passwords. Clients differ in how they render HTML and block remote images, so the same message can look different in each, which matters for tracking pixels and design.
Example
Manual setup for a hosted domain:
Incoming: imap.example.com port 993 SSL/TLS
Outgoing: smtp.example.com port 587 STARTTLS
Username: jane@example.comIf receiving works but sending fails, check outgoing settings and whether the network blocks port 587 or 25. Autodiscovery records can make clients configure themselves.
Common mistakes
- Entering the incoming server as the outgoing server.
- Selecting an unencrypted port because it connects, without checking the security option.
- Assuming client problems are server problems; test the same mailbox in webmail.
Related
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This page is general information written by our editorial team and updated when documentation changes. Servers and providers differ, so test changes safely first. See our editorial policy and disclaimer.