Users of Microsoft Outlook may have observed that some line breaks are stripped from the emails they receive when someone submits their contact form.
This is because (for reasons known best to themselves) Microsoft provides a default setting in Outlook that strips line breaks in plain text emails. The resulting effect will vary based on the content of your email. Microsoft recommend a few solutions, but only two are relevant if you have a version later than 2003:
1) Disable the feature that removes extra line breaks
2) Send the email in HTML format
Considering that the email is a simple notification, it seems more reasonable to simply disable the feature. In Outlook 2010 the path to the setting is as follows:
File > Options > Mail > Message Format > Remove Extra Line Breaks In Plain Text Messages
Uncheck the box and line breaks should no longer be stripped. Please note that if you are using another version this path may be a little different.
Thanks to forum member emartin for helping to identify this issue.
Reference:
How do you hack mail() to get around Outlook's removal of line breaks (webmasterworld.com)
Line breaks are removed in posts made in plain text format in Outlook (Microsoft Support)