element-hq / element-hq/synapse
Synapse emails do not set HELO to an FQDN, meaning they are rejected by some SMTP gateways (including GSuite)
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A-Email-Push
S-Minor
T-Defect
- Dominant language
- Python
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Description
This issue has been migrated from [#8358](https://github.com/matrix-org/synapse/issues/8358).
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**Description:**
Some SMTP gateways require the HELO to be a FQDN
synapse currently sets HELO to `hostname`, hostname is not supposed to be a FQDN
from `man 5 hostname`:
>The hostname may be a free-form string up to 64 characters in length; however, it is recommended that it consists only of 7-bit ASCII lower-case characters and no spaces or dots, and limits itself to the format allowed for DNS domain name labels
in particular gsuite's smtp relay requires this
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