An email client sits between you and a mail provider, so a polished inbox is not enough. The program must authenticate safely, preserve the provider's message model, behave predictably across devices, and give you a workable recovery path. Test with a noncritical account or a small controlled folder before moving important work.
Confirm provider support and authentication
List each account type, including business, personal, school, shared, alias, delegated, and archived accounts. Check whether the provider supports the program and whether administrators allow it. Prefer a current sign-in flow that sends you to the provider rather than asking the program to store the account password.
Google's Gmail client setup guidance recommends the 'Sign in with Google' flow and warns that older programs may not support current security standards. Microsoft's Exchange Online authentication guidance says Basic authentication is disabled and directs compatible POP, IMAP, and SMTP connections to OAuth 2.0 or newer service protocols. Confirm the exact provider, account type, and organization policy rather than assuming a generic IMAP option is enough.
Understand synchronization before importing everything
Decide whether you need the same folders, labels, read state, drafts, sent mail, deletions, flags, and server-side search on several devices. Google's POP guidance explains that IMAP synchronizes across devices in real time, while POP is designed around downloads to a computer and is not a real-time multi-device model.
Run a test matrix: receive, reply, forward, draft, move, label, archive, delete, restore, mark unread, and attach a file. Check the provider's web interface and a second device after every action. Google's recommended IMAP settings show why this matters: sent copies, drafts, spam filtering, deletion, and Trash behavior can interact with Gmail's labels and server rules.
Test search, offline use, and scale
Search by sender, recipient, date, phrase, attachment name, and a message that is not currently cached. Disconnect the network and repeat tasks that must work offline. Reconnect and verify that changes synchronize once, in the correct direction.
Measure startup, search, and folder switching with a representative mailbox size. Check whether the program limits local synchronization by age, folder, or message count and whether attachments are downloaded automatically. A client that performs well with fifty messages may behave differently with years of mail.
Review composition and account separation
Test plain text and formatted messages, signatures, spell checking, reply quoting, calendar invitations, contact completion, large attachments, and accessibility. Verify the From address before sending from aliases or shared mailboxes. Use visibly different signatures or colors if that helps prevent personal and business accounts from being confused, but do not rely on color alone.
Check keyboard navigation, zoom, contrast, screen-reader labels, focus order, notification controls, and whether message content can be read without a mouse. Confirm that remote images, link previews, read receipts, and external content follow your privacy preferences.
Check deletion, retention, and local data
Learn whether deletion in the program deletes from the server, archives, moves to Trash, or affects only a local copy. Test restore before using bulk cleanup. If an organization has retention or legal-hold requirements, the approved system and policy control; a local program is not a substitute.
Identify where local messages, account tokens, contacts, filters, and settings are stored. Mozilla's Thunderbird export guide says its profile export can include accounts, messages, address books, and settings, with a two-gigabyte limit for the built-in ZIP export. Mozilla's profile guidance also warns that a live profile or synchronized folder is not itself a backup and that simultaneous access to one profile from multiple running instances is unsupported. Other programs have different export and restore procedures; test yours.
Review maintenance and exit
Check supported operating systems, update frequency, security advisories, extension permissions, administrator controls, data collection, licensing, support, and end-of-life policy. Remove abandoned extensions and avoid a program that cannot receive security updates on your device.
Document setup steps, authentication type, server behavior, local-data location, backup method, restore test, and how to revoke the connection from the provider account. The selection is ready when mail can be received, sent, searched, synchronized, used offline as required, recovered from a safe deletion test, and exported without exposing credentials or losing important folder state.
Sources
- Add Gmail to another email client — Google
- Deprecation of Basic authentication in Exchange Online — Microsoft, July 16, 2026
- Read Gmail messages on other email clients using POP — Google
- Choose your IMAP email client settings for Gmail — Google
- Export your Thunderbird Profile — Mozilla, March 11, 2025
- Profiles - Where Thunderbird stores your messages and other user data — Mozilla, Sept. 13, 2025