When comparing Canary Mail vs Postbox, the Slant community recommends Canary Mail for most people. In the question“What are the best e-mail clients for macOS?” Canary Mail is ranked 7th while Postbox is ranked 8th. The most important reason people chose Canary Mail is:
You can assign your default signature to an ALIAS for the same account or create an altogether new one.
Specs
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Pros
Pro Multiple Signatures for Multiple Accounts including ALIASES
You can assign your default signature to an ALIAS for the same account or create an altogether new one.
Pro No personal data stored on servers
No access tokens, passwords, attachments or email itself is stored on Canary servers.
Pro Seamlessly integrates with iOS verion
Gone are the days of manual setup of phone email clients! Canary Mail syncs not just your accounts but all of your settings and even signatures on iCloud.
Pro Local email database is encrypted on disk
Canary stores your local email database encrypted.
Pro Gorgeous and intuitive
Pro Pretty Good Privacy or PGP built-in
Pro Clear interface
Pro Forgotten attachment reminders by default
Reminding the user that they forgot to attach the file if they mentioned one in the body of the email is one of the most useful features of any email client and so many don't include this. Postbox is pre-configured to look for certain keywords (attached, CV, spreadsheet, pdf etc) and you can specify your own keywords in addition.
Pro Blocks tracking gifs
Has the ability to block tracking gifs commonly used for read receipts.
Pro One Inbox for all accounts
All messages in one place. But you can select to show only messages from each account either.
Pro Quick Bar for macros
Quick bar allows you to add a variety of content to your message. It will let you reuse URLS in your Sent folder, and autocompletes against canned responses, signatures, and topics.
Cons
Con Missing mainstream features
No functionality for user-defined Gmail message-tagging, or moving/copying to IMAP folders. Might be acceptable in a free app, but not in one with premium pricing.
Con Buggy
It adds random pins to old emails which then stay on top of the inbox list
Con Poor handling of new emails
You sometimes need to wait very long before your email actually gets delivered.
Con Windows moves randomly
When you create a new email, the new windows is often misplaced so that you have to move it to reach the "Send" button.
Con Poor text editing capabilities
The cursor is laggy so you're better off using keyboard shortcuts.
Con Show NO show
It'll show a new email on a counter, but you're not able to view them.
Con No support forum
Support for paid product has no online forums.