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decke / smtprelay

Simple Golang SMTP relay/proxy server
MIT License
455 stars 109 forks source link

Feature Request: Customizable User-Agent Header in smtprelay #131

Closed erseco closed 1 year ago

erseco commented 1 year ago

Hello,

We are using your smtprelay software and have recently run into a challenge with certain servers that block the connection based on the User-Agent header. We've identified that the connection is being blocked because the recipient server doesn't recognize or accept the default user-agent our software is sending.

To overcome this limitation, we'd like to request a feature where we can customize the User-Agent header in smtprelay to simulate being another email client, thus improving our email deliverability.

For instance, we'd like to set our user-agent to mimic Thunderbird:

User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0

Being able to modify the User-Agent would provide us (and potentially other users of your software) with more flexibility and better deliverability when dealing with servers that have stringent rules on client identification.

We appreciate your consideration of this feature request and look forward to any feedback or updates.

Best regards!

decke commented 1 year ago

Modifying the content / headers of a mail is definitely out of scope for smtprelay.