Fix: Email extraction with mailto

[abdullai-t]

Summary / Highlights

This PR adds a fix for the email extraction code for inbound processing to handle instances when the From in the message body includes mailto. Tests have been added for the utility functions.

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Testing Steps (Provide details on how your changes can be tested)

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• [x] I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• [x] I've tested my changes manually.
• [x] I've added unit tests to my PR.

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• [x] I've given my PR a meaningful title.
• [x] I linked this PR to the relevant issue.
• [ ] I moved the linked issue from the "Sprint backlog" to "In progress" when I started this.
• [ ] I moved the linked issue to "QA Verification" now that it is ready to merge.