When comparing Claws Mail vs Seamonkey, 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 8th while Seamonkey is ranked 19th.
Ranked in these QuestionsQuestion Ranking
Pro Has many plugins for extra functionality
Pro Low resource client
Claws Mail is a low resource e-mail client that is often default in low resource Linux distributions.
Pro Clean interface with 5 layout variants
Pro Good support for Google's services
Pro Saves emails in uncompressed readable format
Allows one to read archived emails with a text editor.
Pro Not just an e-mail client
Seamonkey is more than just an e-mail client as it is a full featured web browser as well. This makes for a good app to use for those that dislike having many different apps on their devices as it is a bit like an all in one solution.
Pro Auto imports setting from Thunderbird
For those that would be making the switch from the Thunderbird e-mail client setup is quite easy with Seamonkey as it auto imports all previous Thunderbird settings.
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 Permanent CPU usage
Seamonkey permanently uses CPU (quite a few percents on a Intel i7). On a laptop this causes the fan to run (which make noise) and the battery to lasts less time.