Hi!
This is a new bug since around the 16 may 2025 :
I am sending an email using Brevo transactionnal emails. It includes a vcalendar invite in the following format :
--delimiter
Content-Type: text/calendar; method="REQUEST"
Content-Transfer-Encoding: base64
<base64 of : BEGIN:VCALENDAR .... END:VCALENDAR>
--delimiter
Once it goes through Brevo, the email recipient receive a rewritten base64 invite. Here is the decoded output :
<html><head></head><body><img width="1" height="1" src="https://<myBrevoDmain>/tr/op/IxRzDZq28v5vjE20oP3d64f8hK2Xyc8nIG5zeilWO6IJSL6bZWK2fDsSwEmUz74et8jid6dLZ54jfg8knCRZhCFi9nlAoaYVVlxUeGdOgE9S-wNoy4yQsok3H2owd4AOU0cS-VY_f7E9YJU4NLOVTG_KJXRyn5aeC4kJa-D8ZwfLAOVOEBJRvMepWzSJ3czLI3PvpZO7-hNBCwD6d6bUC3fMTZj4jB3KSAp4_8FObN5lKFXkNQ" style="mso-hide:all"/>BEGIN:VCALENDAR
...
END:VCALENDAR
</body></html>
So Brevo incorrectly injects some HTML into a part which is declared as Content-Type: text/calendar, which breaks it.
Note that this behavior is not happening when the invite is attached this way :
--delimiter
Content-Type: text/calendar; name=invite.ics
Content-Transfer-Encoding: base64
Content-Disposition: attachment; name=invite.ics; filename=invite.ics
<base64 of : BEGIN:VCALENDAR .... END:VCALENDAR>
--delimiter
But I need the first way to attach invite so that they gets auto-added to calendars.
Thanks for reviewing this bug!
Nand