Email subjects containing numbers are scrambled

Hi,

Running CI 3.1 on PHP 7 and I am getting an issue sending e-mails where the subject contains numbers. Rather than reading something like 

Order Summary: XY50/005340

it arrives as:

Order Summary: XY50/=?UTF-8?Q?005430?=

This only happens when the subject line contains numbers, changing the charset to ISO-8859-1 solves the problem but causes issues in the mail body so I've had to comment out the:

PHP Code:

$subject = $this->_prep_q_encoding($subject); 


line in the Email library which has at least bypassed the problem. Some mail clients seem to be able to cope with this but so far I've found that the Outlook App for iOS doesn't so I suspect there are others too.


Dazz.

Just an update, I've been working with the support team of the Outlook App and this looks like a bug in the Outlook app rather than an issue with CI. However, given the popularity of it, I'm keeping that line of code commented out for now until they have resolved it, no ETA as yet though.