Send emails through custom MTA (mail transfer agent), SMTP or POP account (especially transactional)

I would personally prefer to send email, especially transactional emails from my own email MTA/IMAP/SMTP/POP account (in my case Outlook Exchange). We do this with another shared email inbox app called OutPost and we send all our e-commerce website emails through MS exchange now... this has dramatically improved our deliverability.

Even is it was just transactional emails... using a business-grade email sending system is so much better to reduce spam.

Anyone else