On Wed, 17 Oct 2018 at 12:27, K F <fribse2...@yahoo.dk> wrote: > ... What we've seen is some recipients sort of 'goes dark', and they just > timeout on the SMTP connection, and the troubling for us is that it's not > 'small companies' that does this.... But all of the sudden the problem > disappears, sometime after we contact the recipient company, and ask if > they have problems. >
Could be their servers are banning your servers for a time e.g. fail2ban? Is it possible some of your users are sending what gets classed as spam, or to non-existent recipients?
