Getting many emails in pending before 2.16.3 upgrade to 3.0

Your softwareMautic 2.16.3
My PHP version is :7.3
*My MySQL/

Updating/Installing Errors you have pending emails in place.
I am (delete as applicable): Updating 2.16.3 to 3.0
Upgrading/installing via Command Line

Your problem the command line is telling me that i have a lot of emails pending and they recommend firing them out or remove them… i have searched high and low for these pending emails in the spool area and cannot find them…However in the /app/spool/default/Flu.V6JX32.message i can see a file approx 16k bytes… and they look similar to the below…
Is this pending emails and should the be deleted? Any suggestions would be appreciated.

O:13:“Swift_Message”:23:{s:28:" Swift_Message headerSigners";a:0:{}s:26:" Swift_Message bodySigners";a:0:{}s:27:" Swift_Message savedMessage";a:0:{}s:14:" * _userFormat";N;s:15:" * _userCharset";s:5:“utf-8”;s:13:" * _userDelSp";N;s:34:" Swift_Mime_MimePart _nestingLevel";i:4096;s:37:" Swift_Mime_SimpleMimeEntity _headers";O:26:“Swift_Mime_SimpleHeaderSet”:5:{s:36:" Swift_Mime_SimpleHeaderSet _factory";O:30:“Swift_Mime_SimpleHeaderFactory”:4:{s:40:" Swift_Mime_SimpleHeaderFactory

Steps I have tried to fix the problem :Searched hi and low for these PENDING EMAILS with no luck…

Mautic 2.16.3 would spool your emails in:

So this email is from before the update:

After your update the new emails are in:

And this is where Mautic is looking for the emails for sending.
So your old emails are in a folder, where Mautic is not looking anymore. You can move them to the new folder or delete them.