Sieve is a standard system (RFC5228 + extensions) for writing email filters, and ManageSieve is a standard protocol (RFC5804) for modifying these filter scripts. Currently, the “Mail Rules” section in Mailspring only supports client-side filters. These are less useful than server-side rules as they only run when my computer is on (for example, they don’t run if I’m just using email on my phone).
I’d love if Mailspring’s “Mail Rules” section also supported creation of server-side rules via ManageSieve, so that I could modify my email filtering rules directly from Mailspring without having to use a webmail system.
Is Mailspring’s plugin system powerful enough to implement this as a plugin? I’m unsure how extensible the “Mail Rules” code is.
Currently I manage my server-side rules using the Roundcube webmail client. This is fine, but it’s a bit annoying as when I see an email in Mailspring that I want to create a filter for, I need to log in to Roundcube to create the filter.
Fields (in addition to these standard fields, filtering can be done based on any email header):
Manually editing the Sieve script: