Cloudflare Email Forwarding

Delivery incomplete

There was a temporary problem delivering your message to {email address}. Gmail will retry for 47 more hours. You’ll be notified if the delivery fails permanently.

The response from the remote server was:

451 4.3.0 TLS error. YEaKB7FUrPGz

It looks like the Email Routing service has some trouble connecting to the upstream SMTP using TLS. I created a ticket internally and I’ll have a look into it.

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Has there been any progress?

Again, how’s it going?

Kindly and patiently wait a bit more, it’s still weekend around the World :slight_smile:

Furthermore, this is still a beta feature/product so issues might occure randomly.

I have not been able to get this to work with any domain. I have been trying for about a month now. Get a bounce message with 451 4.3.0 TLS error when sending to the forwarding address.

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We have been successful with only one domain

I’m not sure if it makes a difference but this domain doesn’t have a website yet. Just a default HTML page.

Same issue with all of my domains that I’m actively using Cloudflare Email Forwarding with seems like some emails are not being delivered or being rejected by Cloudflare.

Also, emails with attachments (under 20mb in total) are not actually making it to my forwarded address. Can’t figure out the issue.

This is what someone sent me when attempting to email one of the Cloudflare aliases today.

Isn’t your mailbox full? :thinking:

Ask the person if he/she is trying to send you an email with the attachment equal/larger than 20MB …

No, it says email size exceeded, meaning CF is saying that the size of the sent email is too big. My mailbox isn’t even 10% full. The attachment is under 20mb.

@user19033 Cloudflare email routing accepts emails up to 25Mb, including any attachement. Note that due to how emails are encoded, 20Mb might be sent as 25Mb and hit the limit.


thank you for your update. It’s weird how even with under 20mbs of attachments and text of 1kb, the email’s encoding can cause the size of an email to exceed 25mbs. this doesn’t seem to happen with alternative MX handling incoming/outgoing emails (ex. GApps, improvMX, mailway, etc).

I initially was going to ask, “where are the extra mbs coming from??”

But then I did my research on email encoding and learned that “the common [Base64] encoding adds about 37% to the original file size.” The more you know lol. Thanks all!


You are right on point my friend.

And imagine if the software does base64 encoding/decoding multiple times.

It’s not that uncommon, we do it twice when forwarded, one to parse received email and than encode again when sending.

That’s why most email service provider in the backend actually allow more size than advertise to ensure advertised size of email, does work.