HTML-Email with inline attachments and non-inline attachments

Question

What is the correct way to create a HTML-Email with inline attachments and non-inline attachments?

In addition please tell me what Content-Type to use with only inline attachments and with only non-inline attachments.

Until now i did it like this:

MIME-Version: 1.0 [some more headers] Content-type: multipart/mixed;  boundary="myboundary" --myboundary Content-Type: text/html; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit  [html with img cid:my_image]  --myboundary Content-Type: image/png;  name="my_image.png" Content-Transfer-Encoding: base64 Content-ID: <my_image> Content-Disposition: inline;  filename="my_image.png"  [base64 image data]  --myboundary Content-type: application/pdf;  name="my_pdf.pdf" Content-length: 1150 Content-Transfer-Encoding: base64 Content-ID: <my_pdf.pdf> Content-Disposition: attachment;  filename="my_pdf.pdf"  [base64 pdf data]  --myboundary-- 

The mail looks good in outlook. But I noticed that Thunderbird did not display my inline image and shows 2 attachments instead (My image and my PDF). So I did some debugging and noticed that inline images should be sent via Content-Type: multipart/related.

So I changed Content-Type: multipart/mixed to Content-Type: multipart/related and Thunderbird displayed it correct: The image is shown in html and one attachment, the PDF is shown.

I am not sure if this is the correct solution although it seems to work. Is it correct to use multipart/related always (in case if i have inline and non-inline attachments, in case if i have only inline attachments and in case if i have only non-inline attachments)?

Or is the correct way to use one boundary of type related to split the inline attachments and one other boundary of type mixed to split the non-inline attachments?

I hope you can provide me a sample for

1. Email with inline only attachments
2. Email with non-inline only attachments
3. Email with inline and non-inline attachments

Answer 1

Images

Yes, it is correct approach to use multipart/related content type. Here is an example (please note 'Content-Type' and 'Content-Disposition' values):

Example source and detailed info

Here are samples you've requested:

1. Email with inline only attachments
2. Email with non-inline only attachments
3. Email with inline and non-inline attachments

Sample 1: inline only

Subject: Test 01: inline only To: Renat Gilmanov Content-Type: multipart/related; boundary=089e0149bb0ea4e55c051712afb5  --089e0149bb0ea4e55c051712afb5 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable  <div dir=3D"ltr">Lorem ipsum dolor sit amet, consectetur adipiscing elit. P= ellentesque odio urna, bibendum eu ultricies in, dignissim in magna. Vivamu= s risus justo, viverra sed dapibus eu, laoreet eget erat. Sed pretium a urn= a id pulvinar.<br><br><img src=3D"cid:ii_ia6yo3z92_14d962f8450cc6f1" height= =3D"218" width=3D"320"><br>=E2=80=8B<br>Cras eu velit ac purus feugiat impe= rdiet nec sit amet ipsum. Praesent gravida lobortis justo, nec tristique ve= lit sagittis finibus. Suspendisse porta ante id diam varius, in cursus ante=  luctus. Aenean a mollis mi. Pellentesque accumsan lacus sed erat vulputate= , et semper tellus condimentum.<br><br>Best regards<br></div>  --089e0149bb0ea4e55c051712afb5 Content-Type: image/png; name="test-01.png" Content-Disposition: inline; filename="test-01.png" Content-Transfer-Encoding: base64 Content-ID: <ii_ia6yo3z92_14d962f8450cc6f1> X-Attachment-Id: ii_ia6yo3z92_14d962f8450cc6f1  iVBORw0KGgoAAAANSUhEUgAAAUAAAADaCAYAAADXGps7AAAABHNCSVQICAgIfAhkiAAAAAlwSFlz AAALewAAC3sBSRnwgAAAABl0RVh0U29mdHdhcmUAd3d3Lmlua3NjYXBlLm9yZ5vuPBoAAALnSURB ... QCDLAIEsAwSyDBDIMkAgywCBLAMEsgwQyDJAIMsAgSwDBLIMEMgyQCDLAIEsAwSyDBDIMkAg6wK+ 4gU280YtuwAAAABJRU5ErkJggg== --089e0149bb0ea4e55c051712afb5-- 

Sample 2: only attachments

Subject: Test 02: only attachments To: Renat Gilmanov  Content-Type: multipart/mixed; boundary=047d7b41cc5c82ae5d051712c40c  --047d7b41cc5c82ae5d051712c40c Content-Type: text/plain; charset=UTF-8  Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque odio urna, bibendum eu ultricies in, dignissim in magna. Vivamus risus justo, viverra sed dapibus eu, laoreet eget erat. Sed pretium a urna id pulvinar.  Cras eu velit ac purus feugiat imperdiet nec sit amet ipsum. Praesent gravida lobortis justo, nec tristique velit sagittis finibus. Suspendisse porta ante id diam varius, in cursus ante luctus. Aenean a mollis mi. Pellentesque accumsan lacus sed erat vulputate, et semper tellus condimentum.  Best regards  --047d7b41cc5c82ae5d051712c40c Content-Type: image/png; name="test-02.png" Content-Disposition: attachment; filename="test-02.png" Content-Transfer-Encoding: base64 X-Attachment-Id: f_ia6yvl4b0  iVBORw0KGgoAAAANSUhEUgAAAUAAAADaCAYAAADXGps7AAAABHNCSVQICAgIfAhkiAAAAAlwSFlz AAALewAAC3sBSRnwgAAAABl0RVh0U29mdHdhcmUAd3d3Lmlua3NjYXBlLm9yZ5vuPBoAAALnSURB ... gECWAQJZBghkGSCQZYBAlgECWQYIZBkgkGWAQJYBAlkGCGQZIJBlgECWAQJZBghkGSCQZYBA1gWV ywTWDU1tpwAAAABJRU5ErkJggg== --047d7b41cc5c82ae5d051712c40c-- 

Sample 3: inline and attachments

Subject: Test 03: inline and attachments To: Renat Gilmanov Content-Type: multipart/mixed; boundary=001a11c24d809f1525051712cc78  --001a11c24d809f1525051712cc78 Content-Type: multipart/related; boundary=001a11c24d809f1523051712cc77  --001a11c24d809f1523051712cc77 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable  <div dir=3D"ltr">Lorem ipsum dolor sit amet, consectetur adipiscing elit. P= ellentesque odio urna, bibendum eu ultricies in, dignissim in magna. Vivamu= s risus justo, viverra sed dapibus eu, laoreet eget erat. Sed pretium a urn= a id pulvinar.<br><br><img src=3D"cid:ii_ia6yyemg0_14d9636d8ac7a587" height= =3D"218" width=3D"320"><br>=E2=80=8B<br>Cras eu velit ac purus feugiat impe= rdiet nec sit amet ipsum. Praesent gravida lobortis justo, nec tristique ve= lit sagittis finibus. Suspendisse porta ante id diam varius, in cursus ante=  luctus. Aenean a mollis mi. Pellentesque accumsan lacus sed erat vulputate= , et semper tellus condimentum.<br><br>Best regards</div>  --001a11c24d809f1523051712cc77 Content-Type: image/png; name="test-01.png" Content-Disposition: inline; filename="test-01.png" Content-Transfer-Encoding: base64 Content-ID: <ii_ia6yyemg0_14d9636d8ac7a587> X-Attachment-Id: ii_ia6yyemg0_14d9636d8ac7a587  iVBORw0KGgoAAAANSUhEUgAAAUAAAADaCAYAAADXGps7AAAABHNCSVQICAgIfAhkiAAAAAlwSFlz AAALewAAC3sBSRnwgAAAABl0RVh0U29mdHdhcmUAd3d3Lmlua3NjYXBlLm9yZ5vuPBoAAALnSURB ... QCDLAIEsAwSyDBDIMkAgywCBLAMEsgwQyDJAIMsAgSwDBLIMEMgyQCDLAIEsAwSyDBDIMkAg6wK+ 4gU280YtuwAAAABJRU5ErkJggg== --001a11c24d809f1523051712cc77-- --001a11c24d809f1525051712cc78 Content-Type: image/png; name="test-02.png" Content-Disposition: attachment; filename="test-02.png" Content-Transfer-Encoding: base64 X-Attachment-Id: f_ia6yymei1  iVBORw0KGgoAAAANSUhEUgAAAUAAAADaCAYAAADXGps7AAAABHNCSVQICAgIfAhkiAAAAAlwSFlz AAALewAAC3sBSRnwgAAAABl0RVh0U29mdHdhcmUAd3d3Lmlua3NjYXBlLm9yZ5vuPBoAAALnSURB ... gECWAQJZBghkGSCQZYBAlgECWQYIZBkgkGWAQJYBAlkGCGQZIJBlgECWAQJZBghkGSCQZYBA1gWV ywTWDU1tpwAAAABJRU5ErkJggg== --001a11c24d809f1525051712cc78-- 

Quick summary

1. Inline only attachments: use multipart/related
2. Non-inline only attachments: use multipart/mixed
3. Inline and non-inline attachments use multipart/mixed and multipart/related

Update

Here is a very interesting article: Using Images in HTML Email