Mail-in-a-box Guide based on hours of errors/troubleshooting.

The official maintainence guide for Mail-in-a-box can be found here

Note: You should always make regular backups of files.

Help! My emails are going to spam

If you have just created/bought a domain and setup Main-in-a-box to be your mail server but realise that all of your emails are going to spam, this may help you out.
An A record alone is not sufficient for your mail server. You need several TXT records so that GMail or any other email provider can verify the integrity of your mail server. DMARC, DKIM need a TXT record each.
Consider using many free online tools to check your emails. email-tester is a popular online tool that i use often.
The content of your email and the structure and the presence of common spam associated keywords will also affect the chances of it being flagged as spam. email-tester also shows you your spam-assassin rating.
Finally, domain age and domain reputation also play a big role.
If you would be sending bulk emails to GMail users, consider using google postmaster to view analytics

If you have any important data, be sure to always keep a backup
Create a snapshot of your droplet (you can power off the droplet after the snapshot)
Change the owner of your snapshot, see this guide
Resume the transferred snapshot
Change the DNS records to point to the new droplet
Log into the web admin panel at /admin . If there are no errors, everything is good. If there are errors (red text), re-install Mail-in-a-box

Delete the mailinabox directory commonly located at ~/mailinabox
Rename the /etc/nginx/conf.d/local.conf to /etc/nginx/conf.d/local.conf.deleted if you would want a copy
Rename the /etc/nginx/conf.d/ssl.conf to /etc/nginx/conf.d/ssl.conf.deleted if you want to keep a copy
Restart nginx systemctl reload nginx.
Run the installer from the official website and once its done, everything should continue to work as normal.