Review for BorderColors GT by dreadnaut
Rated 4 out of 5 stars
An essential tool for those using many email identities... but not too many.
A few months have passed but the issue described by Drachsi below is still a problem: the configuration dialog does not expand if you have more than a few indentities.
If that's a deal-breaker for you, you can try my experimental version fixing the issue and adding multiple frame styles.
https://bitbucket.org/dreadnaut/bordercolorsgt-dre/
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