Allow Custom Domain as the Sending Address

There currently is no option for changing the sender address from notifications@assuresign.com<mailto:notifications@assuresign.com> to send on behalf of a @custom domain. I've worked with other tools that allow these via SPF configuration.

Adding this functionality would allow for greater trust and less confusion for recipients receiving documents to sign. This is especially important in the current environment where phishing scam awareness is thankfully on the rise and recipients are skeptical of domains they are unfamiliar of.