Currently, https://addons.mozilla.org/about says:

That should be changed to, "If you are looking for add-ons for Thunderbird or SeaMonkey, please visit addons.thunderbird.net."
Edit: new copy
If you are looking for add-ons for Thunderbird or SeaMonkey, please visit addons.thunderbird.net or addons.thunderbird.net/seamonkey.
@caitmuenster the Thunderbird link goes to https://addons.thunderbird.net/thunderbird/ and the SeaMonkey one goes to https://addons.thunderbird.net/seamonkey/, both pages being different so this looks good to me.
Ah, thanks Will! :) So the copy should be changed to:
If you are looking for add-ons for Thunderbird or SeaMonkey, please visit addons.thunderbird.net or addons.thunderbird.net/seamonkey.
If this is your first contribution, please refer to https://wiki.mozilla.org/Add-ons/Contribute/Code on how to get started.
Mentor: @willdurand
@willdurand I would like to work on this bug.
Hi @nabendu82 thanks for your interest , please go ahead.
You need to make changes here https://github.com/mozilla/addons-frontend/blob/master/src/amo/components/StaticPages/About/index.js#L42-L44
Let me know if you need any other help 馃槃
Thanks a lot @nabendu82!
Verified fixed on AMO dev with FF61(Win10).

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Thanks a lot @nabendu82!