email sent with php mail() function, it arrives around 12 hours later?

[dakanadaka]

What is the first thing to do when email which are sent from php mail() function arrive 12 hours later to mailbox.
So yesterday I sent email and after 12 hours or less it arriaves in my mailbox? Where to check first? I have also WHM access.

I think problem was when we updated to 7.1 php version from php 5.6.
Sending from php mail() function works, but sends the email later on like 12 hours later

 

[cPanelMichael]

Hello,

Do you have root access to the server? If so, you can search for the message in /var/log/exim_mainlog to get a better idea of the time frame and actions that occurred after sending the message. EX:

exigrep MessageSubject /var/log/exim_mainlog

You may also find this thread helpful:

Reading and Understanding the exim main_log

Thank you.