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Using Microsoft smtp.office365.com Server, Send fails to all accounts at Comcast.net

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Joe-Diablo
Joe-Diablo
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Using Thunderbird, When I send to someone@comcast.net, I get an error back after about 24 hours. Your message couldn't be delivered. Despite repeated attempts to contact the recipient's email system it didn't respond.

If I send a message using a Web based service or using my Cell Phone, there is no problem with Comcast.

Info from my Sys Admin: 

2 messages that you sent that are listed as “Pending”.  Here is the information on the reason:

Reason: [{LED=421 4.2.0 service unavailable};{MSG=};{FQDN=mx1.comcast.net};{IP=96.114.157.80};{LRT=2/13/2018 8:51:11 PM}]. OutboundProxyTargetIP: 96.114.157.80. OutboundProxyTargetHostName: mx1.comcast.net

So, it does appear to be an issue with your setup rather than Comcast blocking our domain, for example.

Using Thunderbird, When I send to someone@comcast.net, I get an error back after about 24 hours. Your message couldn't be delivered. Despite repeated attempts to contact the recipient's email system it didn't respond. If I send a message using a Web based service or using my Cell Phone, there is no problem with Comcast. Info from my Sys Admin: 2 messages that you sent that are listed as “Pending”. Here is the information on the reason: Reason: [{LED=421 4.2.0 service unavailable};{MSG=};{FQDN=mx1.comcast.net};{IP=96.114.157.80};{LRT=2/13/2018 8:51:11 PM}]. OutboundProxyTargetIP: 96.114.157.80. OutboundProxyTargetHostName: mx1.comcast.net So, it does appear to be an issue with your setup rather than Comcast blocking our domain, for example.