Mailbox & Server Down

[Sami Ketola]

> On 4. Jun 2020, at 18.17, Nicholas Taylor <net20 at cam.ac.uk> wrote:
> 
> Fetchmail connects to your provider's e-mail server as if it were an MUA, then feeds mail to your server's MTA as if it were a peer MTA.  If your provider doesn't allow client connections (by IMAP or POP), then you're right that fetchmail won't help.
> 
> It sounds as though you need to set up some kind of failover for your MTA: a second SMTP server, probably configured to feed your primary SMTP server (which then feeds mails to dovecot), but with a very long queue and many retry attempts.  Then set your Internet-facing router to direct SMTP connections to your primary SMTP server (if it's up), falling back to your secondary server if the primary is down.
> 

SMTP actually has this behaviour built in. Mail Exchanger priorities. 

Just setup your own MX with priority 10 and your providers spooling MX with priority 20 in DNS records and you are good to go.

Sami