Light program (mini MTA?) for system mail (only sending/relay via external server with unattended-upgrades, cron, smartmontools, etc.)

I've come across different names in different places: Light MTA, Remote MTA, Smarthost, etc. Generally, I do not want to install a full-fledged mail server (such as sendmail, postfix, exim), but only send notifications/emails using an existing external ISP/mail provider (such as dismail.de, mailfence.com or others) with unattended-upgrades, cron, smartmontools, my own bash scripts etc from all over the system. Additionally, it would be ideal if there was support for queuing and retrying (an attempt to resend in the event of being offline or temporarily unreachable by the mail provider) So far I've found: - ssmtp - msmtp - s-nail - nullmailer - dma - esmtp But I didn't find any comparison between them. 1. Does anyone know what makes the program stand out from the rest? (positives, negatives, ease of configuration, low resource consumption, etc.) 2. Possibly I missed something and maybe there is another one, better than all those mentioned for Debian? 3. Did I understand correctly that s-nail is also an MUA and bsd-mailx or mailutils is not needed? Maybe others too?