So my wife got a receipt from the people who did our electrical work and she attempted to forward the email to me from Hotmail. There was an error email sent to her inbox that my server would not accept the email because the attachments (well, the email) was too large. I had to add the following lines to my mail.cf file. Actually the “mailbox_size_limit” line was already as seen below – add the line you see below it (allows emails with attachments of about 100 megabyte):
mailbox_size_limit = 0 message_size_limit = 104857600
One hundred megabyte may seem large but it is highly unlikely you will ever get an email close to this size; the email in question contained about a dozen, large .png images.