When comparing Claws Mail vs MailBird, the Slant community recommends Claws Mail for most people. In the question“What are the best e-mail clients for Windows?” Claws Mail is ranked 6th while MailBird is ranked 15th. The most important reason people chose Claws Mail is:
Claws Mail is a low resource e-mail client that is often default in low resource Linux distributions.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Low resource client
Claws Mail is a low resource e-mail client that is often default in low resource Linux distributions.
Pro Open-Source
Pro Has many plugins for extra functionality
Pro Traditional user interface
Pro Clean interface with 5 layout variants

Pro Saves emails in uncompressed readable format
Allows one to read archived emails with a text editor.
Pro Has very strong filters
The filters a much stronger than in thunderbird.
Pro Saves passwords in encrypted format
Pro Has many themes
Pro Also supported on Windows
This makes switching the platform easier.
Pro Good support for Google's services
Pro Free and paid version
Users who only need to use the basic features of the app have a free version available, though it does limit to only 3 sync'd accounts. There is a paid version that does extend functionality and allows for unlimited account but it does cost $1.00 a month or $45.00 as a one time fee.
Pro You can have multiple accounts
In Pro version, you can create an unlimited number of accounts.
Cons
Con Blocks and freezes all the time
Con Saves passwords in plain format
Con Too much bloat
some people dont like the simple design of slypheed so they forked it and created claws mail but it has become so bloated since itsbeginnings.

Con Saves emails in uncompressed format
This takes more space on the HDD.
Con Interface looks old and setup is not easy
The icons as well as the rest of the interface look like an application from the early 90's, with this there is also no easy setup options built in like the more modern e-mail clients.
Con Drag & drop is impossible
Drag & dropping folders and emails between accounts are not possible.
Con Poor import/export of contacts
You can only import your contacts data via CSV, which isn't the most popular choice. Much more convenient ways to do so exist. Even the older Windows Life Mail program is more flexible when it comes to contacts and offers such features as duplicate checks.
Con Collects user data
Mailbird does collect some user data such as user email addresses, names and client use. So for those that are security minded the use collection of this information may not be wanted and can not be avoided.
