When comparing Airmail vs MailMate, the Slant community recommends MailMate for most people. In the question“What are the best e-mail clients for macOS?” MailMate is ranked 1st while Airmail is ranked 2nd. The most important reason people chose MailMate is:
While most email clients support searching content from their To, From and Cc fields, MailMate lets users search down to the different sections of these fields. For example, you can search for the address only, or the name only, or even any one of the embedded headers. Subjects can be searched by prefixes, or by specific words which may be contained within and so on.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Clean interface
Airmail has a very clean and modern interface. On the left side of the screen are the folders (inbox, starred, draft, sent, snooze, trash) and on the right side the email threads for the folder currently being viewed.
Pro Automatically syncs settings between devices
If you are using Airmail in different devices (either MacOS or iOS), you can automatically sync settings through iCloud.
Pro Fast and easy setup process
Even though there's a huge amount of settings available, it's quite easy to get used to each of them and the setup process is very fast and easy.
Pro Consistent interface between devices
Airmail is available for both iOS and Mac, for people who use Apple's mobile devices. And the interface between both platforms is quite consistent, making it easy to seamlessly jump between one and another.
Pro Integrates with multiple third-party services
Airmail can integrate with multiple Cloud services for syncing, creating backups, adding tasks and more. Some of these services include Dropbox, Box, Fantastical, 2DO, Todoist, Wunderlist etc.
Pro Support for VIP folders
VIP folders are for particular senders which you always want to read even when you are ignoring email. The way it works is that you add different senders as VIPs and emails from those senders will always be surfaced on top of everything else.
Pro Extremely customizable
Instead of forcing the user to work with their email the way Airmail developers would want, it allows the user to customize and make the email client work the way they want because of the sheer flexibility of the application.
There's a lot of settings available in Airmail with which you can customize almost every aspect and functionality of the app. In fact, it's very easy to get lost in them and spend a lot of time tweaking and customizing everything to your liking.
Pro Supports Gmail shortcuts
Pro Multiple ways of sorting emails
There are multiple ways to sort emails with Airmail. You can sort by unread, starred, attachments, conversations, dates, and many more criteria. You can even combine different criteria together.
Using these filters makes it extremely easy to quickly find any email you are looking for.
Pro Always keep the inbox clean
Airmail allows users to snooze an email until a defined moment (a few hours later, tomorrow, next weekend, next week, etc.), allowing you to process every email immediately and to always keep the inbox clean.

Pro Supports trackpad gestures
Airmail is able to use trackpad gestures for achieving and deleting mail items.
Pro Extremely powerful search features
While most email clients support searching content from their To, From and Cc fields, MailMate lets users search down to the different sections of these fields. For example, you can search for the address only, or the name only, or even any one of the embedded headers. Subjects can be searched by prefixes, or by specific words which may be contained within and so on.

Pro Keyboard focused
MailMate is extremely keyboard-focused. Almost every action can be configured to be achieved through a key combination in the settings. With the help of the keyboard shortcuts you can easily navigate through thousands of messages to find the one you need.
Pro Markdown support
Markdown is a way to format text quickly using only the keyboard. Different text characters create different text: for example, putting asterisks (*) around a word or group of words will italicize them, while double asterisks (**) will bold that text. Markdown is a basic formatting system that can then be adapted to HTML or other formats.
Pro Clean, no-fuss interface
MailMate's UI is very basic. The icons are limited to some default MacOS standard folder images and the interface is very clean and simple, showing only what's needed without any fuss or distracting colours. Instead, opting for a mostly grey interface, with a sprinkle of some other colours here and there.
Pro Smart folders on steroids
- you can choose out of tenths of mailheaders (several hundreds including virtual headers)
- "<header> is (not) in <folder> <header>" operator which enables you to do cool filters
- each smart folder can have smart subfolders by an user definable key
Pro Reliable
Both MailMate's speed and performance are highly reliable.
Pro Great documentation
The official documentation for MailMate is very thorough and helpful. It covers all options and features in a clear and efficient manner.
Pro Columns (which have gone missing in Apple Mail in Catalina)
Pro Faster
Faster the Mail.app specially if you have many emails
Pro Nice tagging support
One can define tupels of IMAP keywords and tags (which are shown in UI). In case of Gmail one can define triples of IMAP Keywords, Tags, and gmail lables.
(in Thunderbird one can only define the tags, whereas the corresponding IMAP keyword is not user-definable.)
Pro The only mail app compatible with BusyContact in Catalina
Cons
Con Unreliable
There are many issues/bugs with different accounts, including Gmail and iCloud.
Con Serious sync problems
On some IMAP accounts, there are a number of serious sync problems, which otherwise work fine with Apple Mail.
Con Search is buggy and not very powerful
Con Not free
Paid version only.
Con iOS app requires a subscription to enable incoming mail notifications
The iOS app now requires a subscription to enable incoming mail notifications. This makes the iOS app very unattractive and there's little point installing the Mac desktop client for users who want to sync accounts between devices.

Con Copying/moving mails unreliable
Doesn't work most of the time even though the operation is reported as successful. Even has lost emails when moving. Support was not too much use either.
Con Rather expensive
Con Inability to turn off auto-creation of labels
Version 3 does not allow it while version 2 did.
Con UI is a little busy
Con Has the "slow typing" bug
When composing an email, Airmail can respond very slowly to keystrokes. Customer service refuses to acknowledge this problem, responding that it's "not real" - which is a very odd response, to simply refuse to acknowledge the customer's experience.
Con Hard to master
For occasional users who only write emails to friends and loved ones, MailMate's features may be a bit of an overkill since it's designed for power users who spend a lot of time writing and reading/organizing emails.
Con Not so "native" Gmail support
Because it's more IMAP native, and Gmail uses some non-native IMAP stuff (according to MailMate's documentation).
Con Ugly!
Seriously dated UI and looks too much like Apple Mail
Con No POP or Exchange support
MailMate supports IMAP and IMAP only, there's no POP or Exchange support.
Con A little steep price
$50
