Add a CTA (Call to Action) button to your MailChimp RSS emails.

functions-01.php

<?php

// do not include the opening tag

// Disable the Read More link added by Send Images to RSS
add_filter( 'send_images_rss_excerpt_read_more', '__return_false' );

functions-02.php

<?php

// do not include the opening tag

add_filter( 'send_images_rss_excerpt_read_more', 'leaven_change_read_more_cta', 10, 5 );
/**
 * Modify the Send Images to RSS excerpt "read more" link output to be a button in MailChimp.
 *
 * @author Robin Cornett
 *
 * @param $output string        final output for "read more" text
 * @param $read_more string     "read more" text set on plugin settings page
 * @param $blog_name string     the name of your site
 * @param $post_name string     the post name
 * @param $permalink string     URL for the post
 *
 * @return string
 */
function leaven_change_read_more_cta( $output, $read_more, $blog_name, $post_name, $permalink ) {

	// set your colors here
	$button_color = '#2a717a';
	$link_color   = '#ffffff';

	// for a full width button using your Read More text, you shouldn't need to change this
	$output  = '<table border="0" cellpadding="0" cellspacing="0" style="background-color:' . $button_color . '; border-radius:5px;" width="100%">';
	$output .= '<tbody>';
	$output .= '<tr>';
	$output .= '<td align="center" style="color:' . $link_color . '; font-weight:bold; line-height:1.5; padding-top:15px; padding-right:30px; padding-bottom:15px; padding-left:30px; margin: 24px auto;" valign="middle"><a href="' . $permalink . '" style="color:' . $link_color . '; text-decoration:none;" target="_blank">' . $read_more . '</a></td>';
	$output .= '</tr>';
	$output .= '</tbody>';
	$output .= '</table>';

	return $output;
}

mailchimp-rss-block-01.txt

*|RSSITEMS:|*
<h2 class="mc-toc-title"><a href="*|RSSITEM:URL|*" target="_blank">*|RSSITEM:TITLE|*</a></h2>
*|RSSITEM:CONTENT|*

<table border="0" cellpadding="0" cellspacing="0" style="background-color:#2a717a; border-radius:5px;" width="100%">
	<tbody>
		<tr>
			<td align="center" style="color:#FFFFFF; font-weight:bold; line-height:150%; padding-top:15px; padding-right:30px; padding-bottom:15px; padding-left:30px; margin: 24px auto;" valign="middle"><a href="*|RSSITEM:URL|*" style="color:#FFFFFF; text-decoration:none;" target="_blank">Read *|RSSITEM:TITLE|* on my site.</a></td>
		</tr>
	</tbody>
</table>
*|END:RSSITEMS|*

mailchimp-rss-block-02.txt

*|RSSITEMS:|*
<h2 class="mc-toc-title"><a href="*|RSSITEM:URL|*" target="_blank">*|RSSITEM:TITLE|*</a></h2>
*|RSSITEM:CONTENT|* *|END:RSSITEMS|*