Spam sent only when mail app is opened

[pencilandpaper]

When the mail app opens on my wife's iphone6 i get spam email.

The email address is connected to our isp.
I changed the password. No effect.
The email which includes your standard spam text is only sent to the email addresses of people who have an email sitting in the inbox on the server. I'm not sure if i've made that clear.
So when the mail app opens a spam email is sent only to the emails that she has received then and there.
Not to the rest of the inbox or contacts.

The spam is not sent from her windows computer or when using web based mail only when the mail app on the phone opens.

I set her up with a gmail and routed all her mail through it as it was driving me crazy but every now and then the mail app is activated and the spam goes out.
All the searching i've done says there are no viruses or ways this could be possible and maybe i've overlooked something so i would appreciate any feedback.
The phone is not jailbroken and doesn't contain any dodgy apps beyond the standard stuff like facebook etc.

 

[J. A.]

Welcome to iPhoneForums, pencilandpaper!

This behaviour shouldn't be caused by the iPhone itself. It's just mirroring/syncing the server, where emails and accounts settings are stored. Changing the password was a great idea. Here's what you can do as well:

Make sure no one else has been given access to the account. It's possible you'll need your ISP's help to find this out.

If you can access the server settings of the account online, through a browser, login and take a look at them. Check any settings related to auto-reply, or rules, such as vacation messages.

Hope that helps.