When comparing Trillian vs Mozilla Thunderbird, the Slant community recommends Mozilla Thunderbird for most people. In the question“What are the best IRC clients for Windows?” Mozilla Thunderbird is ranked 9th while Trillian is ranked 21st. The most important reason people chose Mozilla Thunderbird is:
Mozilla Thunderbird offers a huge amount of [extensions](https://addons.mozilla.org/en-US/thunderbird/) to expand the usability and options of the client.
Ranked in these QuestionsQuestion Ranking
Pro In-house server support
You can set up a dedicated server to hold your communications. Great for businesses that want to build their own infrastructure.
Pro Multiple networks in one place
Among them Yahoo!, Facebook, Skype, Google, AIM, ICQ, XMPP, MSN. You can have multiple accounts associated with each service.
Pro Group chat
Trillian to Trillian group chat is available.
Pro Large assortment of plugins available
Mozilla Thunderbird offers a huge amount of extensions to expand the usability and options of the client.
Pro Available on Linux, OS X and Windows
Pro Very reliable
Version after version, Mozilla Thunderbird works as expected.
Pro Free (as in freedom and beer)
Pro Good filtering system
Mozilla Thunderbird offers a flexible filtering system with the ability to set flags and read/unread, as well as sort/assign to new mail directories. There are also numerous plugins available to assist in the filtering.
Pro Lightning Calendar and Address Book integration
Pro Consistent and involving a moderate learning curve
The app design of Mozilla Thunderbird has not changed significantly since its beginning, making its learning curve almost non-existent.
Pro Great flexibility
More options and extended settings than most power users could dream of. Get it working how YOU want.
Pro Tabs for navigation
Pro Send large files easy
Install pCloud plugin for Thunderbird and your files (upto 20 GB free storage included) will be received as download links
Con Supports all dead services.
Con Development slowed to only focus on stability and security
Mozilla Thunderbird has slowed down its development of features to only focus resources on security and stability.
Con Terrible integration with macOS
Simple things - drag/dropping pictures doesn't work, for instance.
Con Outdated interface
Thunderbird's interface is very outdated and unpleasant. It feels more like a Windows XP application than like a modern MacOS one.
Con Subject lines can (temporarily) disappear from the list
This is sporadic behavior.
Con Serious bugs
Clicking on a subject line can bring up the wrong email.