5 ਤਾਰਿਆਂ ਵਿੱਚ 4 ਮਿਲੇ

If one mail failed (due to wrong email/else) during schedule process that stuck another last all mails in outbox....if anyone facing this issue please reply for solution.

ਇਹ ਸਮੀਖਿਆ ਐਡ-ਆਨ (6.3.1) ਦੇ ਪਿਛਲੇ ਵਰਜਨ ਲਈ ਹੈ। 

I agree that this is annoying.

Unfortunately, it's a Thunderbird bug, not a bug in Send Later. I reported it to the maintainers of Thunderbird almost six years ago: https://bug635044.bugzilla.mozilla.org/show_bug.cgi?id=749654 . Unfortunately, they still haven't fixed it.