Thank you for the reply. Actually there are 7 emails sent by the user. 2 emails are delivered successfully. 5 are missing. All are having the same log with virtual. At present I might not be able to change those settings.... Is there any way to verify they are delivered to them or not? do we have any logs to verify the same? 

On Tue, May 5, 2020 at 9:16 AM Zhang Huangbin <zhb@iredmail.org> wrote:

> On May 5, 2020, at 4:06 PM, Kishore Potnuru <kishore.reachme@gmail.com> wrote:
>
> May  5 07:35:21 testserver postfix/virtual[29843]: EB6A2206818: to=<selfemail@testing2.com>, relay=virtual, delay=0.05, delays=0.05/0/0/0, dsn=2.0.0, status=sent (delivered to maildir)

According to the log, this user is using Postfix builtin transport "virtual" as LDA, not Dovecot LDA. Fixing this should get your email delivered correctly.

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Zhang Huangbin, founder of iRedMail project: https://www.iredmail.org/