I am an editor for a math journal. When I select and invite a reviewer to referee a paper the journal's management software automatically writes and sends an email invitation to that reviewer.
For a couple of recent papers where I was having trouble getting reviewers to accept an invitation I started sending a manually written email (from my university email address) to the potential reviewer asking them to consider reviewing the paper,
My response and acceptance rates are much higher when I do this, which is great, but I worry if I am being overly pushy this way, or if emailing reviewers directly is outside the norm. When I get requests to review papers myself, I almost never get a manually-written email from the editor, just the auto-generated one.
So is it OK to send a manually written email to potential reviewers, when the journal already sends them an autogenerated email invitation? This manually written email would be in addition to the autogenerated one.