What might be the reason for a email delay of 2 days

[nn2000]

I sent an email to my own email address of the other domain on Friday. I did this many times before for personal reason. This time I did not receive the email until today (Sunday) noon. What might be the reason for the delay?

 

[fsardis]

network traffic or perhaps some server went down for a short period

 

[FlyingPenguin]

Email is never guaranteed to be delivered promptly. It usually is, but I've seen email delayed as long as a week.