Re: [mailop] Cannot send messages to Google Mail users

2024-04-25 Thread Matus UHLAR - fantomas via mailop
On 24.04.24 17:00, Simon Branch via mailop wrote: Thank you everyone for your input. After reading the various comments, I decided to try creating a connector in 365, specifically for emails going to the Gmail domain. Funnily enough, the emails are now delivered to Google's servers, alb

Re: [mailop] Cannot send messages to Google Mail users

2024-04-24 Thread Simon Branch via mailop
Firstly,Thank you everyone for your input.After reading the various comments, I decided to try creating a connector in 365, specifically for emails going to the Gmail domain.Funnily enough, the emails are now delivered to Google's servers, albeit the messages end up in users spam folders, as oppose

Re: [mailop] Cannot send messages to Google Mail users

2024-04-24 Thread Mark Alley via mailop
On 4/24/2024 10:04 AM, Al Iverson via mailop wrote: Is disabling IPv6 an option here? A prior poster suggested as such, but I don't know if that was just a general suggestion or if that's actually possible in O365 settings. But if you can yes, try sending outbound mail only via IPv4. A "wel

Re: [mailop] Cannot send messages to Google Mail users

2024-04-24 Thread Al Iverson via mailop
Is disabling IPv6 an option here? A prior poster suggested as such, but I don't know if that was just a general suggestion or if that's actually possible in O365 settings. But if you can yes, try sending outbound mail only via IPv4. A "well known secret" is that Gmail filters mail from IPv6 c

Re: [mailop] Cannot send messages to Google Mail users

2024-04-24 Thread Mark Alley via mailop
I've also seen Google provide this error when a domain had a spammer/phisher attempt to spoof said domain several hundred thousand times. Since Google saw their domain in the RFC5321.Mailfrom, even though the messages weren't authenticated and were rejected as per their DMARC policy, the domain's m

Re: [mailop] Cannot send messages to Google Mail users

2024-04-24 Thread Stuart Henderson via mailop
On 2024/04/24 12:04, Matus UHLAR - fantomas via mailop wrote: > Make sure nobody did spam/mailbomb from your domain while having matching > SPF/DKIM. I guess that could include forwarding of spam messages or > creating mail loop etc. AFAIK forwarding mail into gmail is generally not good for your

Re: [mailop] Cannot send messages to Google Mail users

2024-04-24 Thread Matus UHLAR - fantomas via mailop
On 24.04.24 07:28, Simon Branch via mailop wrote: For the past 2 weeks, we have been unable to send mails to any gmail users, nor any email domains hosted on Google's mail servers. We are using Microsoft 365. So I assume you send your mail through microsoft/outlook servers, you can't your ou

Re: [mailop] Cannot send messages to Google Mail users

2024-04-24 Thread Florian Effenberger via mailop
Hi, Marco Moock via mailop wrote on 24.04.24 at 10:41: That is fine, the host has 2 addresses attached. Both have a PTR. I don't see a DNS issue. I just had a look at one of my friend's MX and can confirm that the PTR was correct there as well - but disabling IPv6 interestingly helped to av

Re: [mailop] Cannot send messages to Google Mail users

2024-04-24 Thread Marco Moock via mailop
Am 24.04.2024 um 10:08:53 Uhr schrieb Marco Davids via mailop: > However, the IPv6-address in the error below resolves to two names: > > ;; ANSWER SECTION: > 0.0.7.0.0.0.0.0.0.0.0.0.0.0.0.0.b.1.6.2.3.0.4.f.1.1.1.0.1.0.a.2.ip6.arpa. > 3165 IN PTR mail-cwxgbr01on20700.outbound.protection.outlook.c

Re: [mailop] Cannot send messages to Google Mail users

2024-04-24 Thread Marco Davids via mailop
Not sure if this helps, but Gmail requires forward and reverse DNS for IPv6 to match. Like this (example is from our own setup): ;; ANSWER SECTION: e.1.7.0.0.0.0.0.0.0.0.0.0.0.0.0.a.1.e.7.0.0.4.f.1.1.1.0.1.0.a.2.ip6.arpa. 3379 IN PTR mail-db8eur05on2071e.outbound.protection.outlook.com. ;; A

Re: [mailop] Cannot send messages to Google Mail users

2024-04-24 Thread Florian Effenberger via mailop
Hello, Simon Branch via mailop wrote on 24.04.24 at 09:28: /550 5.7.350 Remote server returned message detected as spam -> 550 5.7.1 [2a01:111:f403:261b::700 19] Gmail has detected that this message;is likely suspicious due to the very low reputation of the sending;domain. / /To best protect