So my user signs up from the Android App on his phone and after sign up is successful I trigger a mail to be sent to the signed up email address with an Activation Passcode from my PHP script. Here is the line of code that I use which is pretty trivial.
mail($to, $subject, $message, $headers);
The mail is sent correctly every time to the correct email address but the problem is the email shows up in Gmail or Hotmail or Yahoo in more than 10 minutes. That kind of a latency for receiving an Activation Code for the App "to me" is unacceptable.
What can reduce this latency and make this if not instanteneous but a lot quicker. Any ideas.
Thank you all for your help!!
I had this issue with GoDaddy shared hosting, using their SMTP server. It was because the SMTP server was a shared, open relay, and with the volume of messages passing through it - there is a delay of roughly 10 minutes as well.
Are you on shared hosting/GoDaddy? What SMTP relay are you using?
EDIT: After researching this thoroughly very recently, I have found that there is no way to deliever a high quality of SMTP service (i.e. < 10 minutes for an email) to my audience on GoDaddy shared hosting. This is incredibly frustrating. Looks like the options are to buy dedicated hosting from GoDaddy (~$300/year), or to switch providers.
On top of everything else, the receiving end may be using greylisting, which basically bounces an email on the first delivery attempt, on the theory that spam sources won't bother retrying, while a legitimate server WILL re-try after a few minutes.
most likely it is your server, perhaps you have a anti-spam program or anti-virus program? If you are on a shared environment there may be a que.
I'll guess you're using some shared hosting which probably is using some q system and therefor the delay... If your really picky about getting your mail delivered at once i would recommend dedicated hosting
Try this service guys...awesome API integration. www.postmarkapp.com After lot of searching I integrated my Android App Account Activation email service to Postmark and works like a breeze. Mails started getting sent to users instantly and the latency was reduced from stupid Godaddy's 10 mins or more to within a minute. I highly recommend it.
来源：https://stackoverflow.com/questions/4044502/php-mail-function-sends-the-email-but-it-takes-more-than-10-mins-to-show-up