I can send emails to (some) adresses with this command:

echo 'test' | msmtp xxxxx@gmail.com

it also works with some other addresses, but not with any of the temporary ones I tried out.

Anyway, here are the relevant conf files

account gmail
host smtp.gmail.com
port 587
protocol smtp
auth on
from xxx@infocalypse-net.info
user xxx@infocalypse-net.info
password xxxxxx
tls on
tls_starttls on
tls_trust_file /usr/share/ca-certificates/mozilla/Thawte_Premium_Server_CA.crt


account default : gmail

; For Unix only.  You may supply arguments as well (default: "sendmail -t -i").
; http://php.net/sendmail-path
sendmail_path = "/usr/bin/msmtp -t"

So shouldn't wordpress now use that to send emails? I can send to some addresses with the manual command, so shouldn't it work? Well it doesn't. Wordpress doesn't do anything, and all of the various plugins I tried don't work either.

Edit:

I tried changing the flags in my php.ini
"/usr/bin/msmtp -t -i" doesn't work either, nor do any of the other ones I've tried.

According to the msmtp docs, 'sendmail' mode is enabled by default, so it should be compatible. I'm just not sure if I need to do something special to make it work.

Why don't you install postfix and let your server send emails itself?

Because I don't want a mail server running on it. I've already changed the mx records to google's. It's a security issue having a mail server running, and it uses up memory. Besides, I can send email fine with this already. It's the mail() function that doesn't work.

It's not that much of a security issue having a mail server installed, don't have an open really, hell don't open port 25 to incoming connections if you're that worried (although you won't get bounce messages). As for memory my postfix is using around 1.5MB of memory on a 32 bit ubuntu distribution. Nothing to worry about.

If you really want to use smtp on an external server for PHP you should consider using http://pear.php.net/package/Mail if you still want to use the inbuilt mail() try enabling php error logging and see if it's dumping an error message. You could also check /var/log/syslog I don't know if msmtp logs it's messages there but it'll be somewhere in /var/log

For anyone who reads this; I solved the problem. What was happening is this:

msmtp is configured to only allow read/write permissions for the user who owns the conf file, ~/.msmtprc

If you want apache to be able to access the conf file, you need to copy ~/.msmtprc over to /etc and give the user running apache read access. Making sure to rm the file in ~/ once you've done that.

Couldn't be any simpler, yet nowhere I looked told me this.